What do you want out of the relationship? If she doesn't want the same thing, which it seems she just wants to have fun, then you can either live with it or move on. Either way is your decision, either way is hard.
She can't come out to her family about you or anything else, she would lose them, it's that simple. JW will expel anyone that is not associating with other JW's.
She would have to love you enough to give up all her family and friends. That's a big ask and you don't understand that aspect of her life, it's easier for her to hide than to do whatever she does with you.
Be honest with her and yourself, you are part of that life, as long as she wants to go to the Kingdom Hall and pretend she is a Witness, you can't be part of that part of her life and the other side can be crazy because if you've lived that long inside a cult, anything going on outside is going to be exciting and new. She's mentally a 16 year old without parents - I've been there.
If you're looking for a monogamous classic commitment then you're probably not going to get it. She won't marry you because she can't tell her family. She won't stay with you because it's too much fun moving around and she has extreme fears about being pinned down again.
If she was married and they are JWs, you have no idea the mental and psychological abuse women go through within the cult. That is the first thing that she has to overcome.