wow, Oz i really feel your pain. Im only a bible studentmyself and i see many flaws in this faith. Im unsure wether to carry it on, but it seems doubtful that i will :) i have been studying a little over a year now.
I would suggest (as friendly advice) to challenege her about somethings as you said you have. Keep at that, and if she really does love the bible and reads it and knows it well, you can tell her this scripture: Proverbs 27:6. Try to get your head around that. she probably wont, until you explain it to her.
Proverbs 27:6 basically means, that the wounds inflicted by a lover are faithful, (it hurts, but your doing it to help her for the greater good) and the second part of the verse then says that but the kisses of a hater are things to be entreated. So that basically means that you could quite easily just say to her, oh its ok, just carry on dear. do as you please. Which is obviously wrong. Im sure she will understand that you are doing this to help her see the truth... behind the truth.
^_^