i was at my rav’s house last week and we were discussing hashkafah and kiruv and he told me that a lot of questions and rebellion against yahadus comes from trouble in a person’s life. id say that was spot on here. your priority, if you want her to eve become frum, should be to help her out of her current situation and find her a more stable living environment. someone who is under that much pressure and stress and has such a messed up life doesnt particularly care (at least on the surface…youre right about her wanting to be frum because she keeps coming back) about being frum because her priorities are different from yours. as far as shes concerned “self reservation” is all that matters. once you remove her from her current situation her priorities will shift back to what she really wants.
as far as her being resentful that youre prying in her personal life and meddling about…if you manage to arrange something that is in her best interest then she wont mind. go for it. its your best shot