So she "likes the brothers and sisters at the hall and they all love her, and is not having any personal problems", other than the fact that she contemplates suicide, is very depressed, and has pulled away from her friends. One of these things is not like the other.
You sound like a good guy and you care about your daughter and that's great. Your daughter is likely to face a lot of pain because if she truly wants to be herself and be free, she doesn't have the luxury of faking it like you and she doesn't have a good example of taking that stand. She doesn't just need one PIMO friend, you're fooling yourself. She is suicidal. That's what you wrote. She may feel trapped, or like she's worthless because the cult she's been kept around makes young people feel worthless. So she's already going through pain, you can't save her from that nor is it your place to.
Your best plan of action is to let her be her, support her in that, be a shoulder to cry on, point her to professional help outside of the cult, etc. If she wants worldly friends she should go get some. If she wants to date a worldly boy she should go do that. Be careful that you don't let your own compromised position with the cult impact how you steer her in these matters. She's got a long life ahead of her and she will have to try to pull off a fade unless and until her real life on the outside catches up to her, which it likely will because you're in a cult where that's kind of their modus operandi. You got to skirt by and you're lucky. Some are. Many are not. With her being so young she may likely have a hard time playing the long game. She could move far away and start over if she wanted, but of course she won't be able to be around you guys or the rest of the family.
Maybe it's just me, but although I see you as this loving dad with a kind heart I (fairly or unfairly) worry that you're a little too deep into the JW weeds to fully see what your daughter is saying to you. There were giant red flags of depression and suicide and that's as things are today. I know you're worried that if she left totally and was shunned that it would get worse but it might get better. My depression and anxiety nearly vanished when I put that cult behind me and disassociated. I haven't had suicidal ideations since leaving that garbage behind.
I really hope your daughter finds places like this or the exjw reddit or videos online or podcasts like I do or something so that she can feel less alone and start to find herself. I firmly believe that one of the biggest reasons for depression in life is living a life that is inauthentic and she's been doing that. If she can live a life true to who she is she will be far happier than playing games with cults.