Hi Sven,
A voice of experience speaking here; I was baptised and became interested in a girl who was not one of Jehovah's Witnesses. (I plan to relate my story here one day.) I am no expert. I repeat: I am no expert. But your situation sounds so familiar I just had to post my thoughts.
Firstly, a couple of basics:
1) Do not get baptised.
Not only would getting baptised be an enormous risk (she could shun you when you were disfellowshipped), but it would also destroy an important advantage which you currently have. Submitting to the cult would reinforce, in her mind, the view that all good, honest-hearted people can see it is the truth and only serve to make it harder for her to think along the right lines. While you are a "worldly person" (someone who is not one of Jehovah's Witnesses), you can continue to provoke an uncomfortable thought in her mind - that there are entirely good and decent people outside of her religion. If you want to help her instead of just getting her for yourself, making it possible for her to get out should be your goal. Life inside her current world is not something you want long-term.
2) Do not tell her you have been posting about the religion, or her, on the internet.
She has been trained to view anyone who has an insider's knowledge of the religion and that chooses to criticise the Watchtower Society as evil. She will likely believe that "apostates" have fed you false information and deceived you, and then tell you so and choose to stop contact with you in case you pollute her.
So, with those two fundamentals out of the way, how do you work out where to go from here?
Before you take any further action or say anything new to her, I suggest you work out in your own mind how much you are willing to risk losing in order to give her a chance at getting herself out. Is it possible that she will free herself? Yes. But it is also possible she never will. How long will you wait? It would have to be at least months; possibly years. Is she worth it?
If you're not willing to place a relevant portion of your lifetime and emotional reserves into this, then walk away. (In that case, I suggest you inform her you have found researching her religion interesting but that you are not comfortable with its translation of the bible which deliberately misrenders key scriptures, you can't make yourself submit to men who demand that their followers submit to their current set of doctrines and rules instead of what you have read in the bible that Jesus taught and that you believe each of us has to be honest with ourselves and do what is right. Wish her all the best and part on your separate ways. You never know - this all-or-nothing approach might just trigger something, but don't count on it.)
If you are willing to wait for her, then you will need a good deal of patience and self control to give her the best chance of freeing herself...
Thinking back to when I went through my process of "temptation", doubt and research, I can see encouraging signs in what you have related about her here. She has already gone way outside of her supposed boundaries by talking with you for such long sessions, kissing you and talking about things in what you believe to be an honest way. I feel that her comment that she has never told anyone half as much about her feelings as she has told you is particularly significant. If she can see that your discussions on the topic of religion are honest and fair-minded, this is a very good thing. And she'll follow you wherever you go (if you were to become a JW)? Sounds like she is, indeed, in love, which is probably the only thing for a lot of people that could possibly motivate some real thinking.
I got to a stage where I'd felt close to a girl for some months, and I couldn't really imagine her ever wanting to become one of Jehovah's Witnesses. For some weeks I was hoping that she'd end up having a bible study with JW's where she lived and get baptised which would have made her "available" to me. If I'm honest with myself, my doubts only really resurfaced in my mind because, all of a sudden, there was something worth having if they were valid. The thing is, maybe the girl you're interested in never really had doubts before.
I never said to the girl that I wanted to break anything off as we hadn't got together. By the time I knew for sure that she wanted to get to know me better so that we could try to be with each other, my doubts were already too active to be ignored and had motivated me to start my research. I told her that I couldn't be with her if I was to remain one of Jehovah's Witnesses as I wanted to do what I believed was right and that it wouldn't be fair on her either, due to the different way of life. I then told her I had doubts, and that I wouldn't be surprised if I stopped believing. But I didn't open up about what my doubts were. I needed time (months) to myself to sort things out, without discussing what it was I doubted with her.
So, you see, I had already done some critical thinking at that stage. I suspect your girl has, too. But is she open enough to act on those thoughts? Now there's a question.
Moving forward, don't give the impression that you're seriously considering becoming one of Jehovah's Witnesses. If she thinks you might take the plunge one day, she'll almost certainly make herself wait for you. It is so important that you keep your relationship as loving and as close as possible without being pushy or inferring you'll ever get baptised. As long as she has you as a possibility that's currently out of reach, she won't be happy where she is if she really does feel the way you think she does.
On the other hand, you need to appear open-minded. As you have already discussed religion, you will need to be willing to ostensibly consider what the Watchtower Society tells her to teach you.
I think the best way for you to get her thinking processes going is to pick a topic that you know is a weak point in the Watchtower's set of doctrines. Let her do the JW teaching bit; listen; show reasonableness; tell her you'll take whatever literature is relevant and look at it; tell her you may not agree with all of it; tell her you'll compare it with what the bible says. Then, when you feel is a good time (this could be days or weeks later - don't push it), gently allude to something that poses the religion a problem. Don't go overboard and try to smash the teaching to pieces. Just infer that you don't quite see how things match and that you're still looking at it. She probably won't be able to resist looking up whatever it is herself so that she can be ready to "correct" you. Maybe it will start something.
For example, I understand the Society's brochure on the trinity is full of out-of-context quotes of various people and contains misleading information about historical beliefs. (I haven't checked this myself; just read about it sometime ago.) If you wanted to use this, you could strike up a discussion about how different the JW stance on the trinity is from other Christians and ask why. If she doesn't give you the brochure, ask where she gets her information from and it's likely she'll give you a copy. Don't give the impression you're lapping it all up and believe every word she says. Remain objective and fair. Tell her you'll read it and look up the scriptures and references. Then continue to be there for her. Keep close. Maybe show a nice, modest gesture by way of a complimentary email or card. (A Valentine's Day card or gift would likely not be a good idea as it could upset her conscience again.) At some point, when you're discussing the trinity again, mention that you looked up so-and-so and didn't see how it made sense because it seemed to be saying something different. If she asks you what it says, then you can tell her. Don't force it. Move on to the next thing. Then, another time, do the same thing again with a different section and quote from the brochure. Who knows? She may even ask to see the references which have been misquoted for herself. (This would involved purhasing/borrowing some original material for reference, which is why so many Witnesses never find out.)
This is just one idea, and possibly not the right one for you/her. Run something by us before you use it, or post back for more suggestions.
There are people here who have been married for half of their lives as witnesses and one member wants to get out. They know that person better than anybody in the world, and they're experts on witness beliefs and fallacies, and they still have no idea how to help them out. That's because the process cannot possibly work if there is an external pressure on the person concerned. If anybody had tried it with me I'd have gone running back in a heartbeat, cut that person off, and not miss a meeting for five years. This is the nature of her attachment. There is nothing you can do. If she thinks she loves it and wants it, you must let her work out for herself why she's wrong. There is no way to tell her.
And there it is. You cannot tell someone something and expect them to believe it if they're too scared to think. You have to allow her to have her own reaction; but maybe, just maybe, you can be the catalyst. If you proceed, I hope she is as logical a thinker as you say she is.
Post back here as much as you like. Take your time in thinking about what you will do, and don't rush yourself or her. All the best, whatever you decide to do.