Quick point: You mentioned that she was only "inactive" yet she had left her husband and taken up with another man and bearing his child. My assumption then is that she will most probably be disfellowshipped in the future (especially since it appears the Elders were already on the "side"of the former husband and didn't have her interests at heart or they would have mentioned something about his past to her). Therefore, if she is Disfellowshipped you should factor this in because during that time (and assuming that she doesn't get reinstated) she is likely to be exposed to a lot of things that are going to bolster any info that you may choose to point her too, here on this website, silentlambs, H20, WT Observer, etc. etc. and therefore what I am saying is that her likely DF'd status may decrease the chance (and your fear) that she is going to return to the fold and blow your cover. (If I got the gist of what your concern was.)
Turning to actually helping this person, as you have already observed much or perhaps most of her trouble has nothting to do with the religion and so if you wish to help her you should help her to get this non-religious help, i.e. counseling, perhaps medical treatment for her depression, and so on and stay completely out of the realm of religion for the time being.
I advise you to do this part FIRST and then take a temperature check with where she stands at that point. In the meantime and by the time that is accomplished you can see what problems she is having. Perhaps she will have come to her own conclusions about JWs or will be indicating to you her strong desire to return. And hopefully many of these other non-religious related problems will be better.
Then you can decide at that time whether you wish to share any of the promethian fire with her or let things be.
In any case, since she has these other non-religious problems, you do not want to expose her to these other things in such a mixed up state. It will be and is hard enough to get a level headed JW to even consider this stuff so even more so you don't want her to be in a state of depression, anxiety, etc. due to other non-religious things as these things will affect her judgement and you want her to be in the best state possible before you begin to unload the other stuff on her.
All of this is a way for you to begin helping her immediately, while keeping yourself safe (since no claim of your sharing apostate, etc. info with her could be raised), and buying time for you to decide when it comes to the next phase what you will choose to do.
In the end though follow the Golden Rule and also do what you believe to be the KIND thing to do no matter what personal consequences it may have for you. Being a true Christian means sometimes you have to feel the fire a bit.
--Eduardo