Hi T.,
I am a stepmom, too, and I know its a touchy subject as to what you can talk about with your stepchild. If you are close, I'd say, you need to follow your heart and give your stepdaughter any information you feel she should know.
Be aware, you are probably in a losing position, here, as someone will not be happy with you answering these kinds of questions. My stepson's mother was upset with my husband (and me) because he discussed her son's schooling with me before discussing it with her, even though he lives with us full time! So, her mother won't be happy no matter how well or appropriately you handle it. Her mother will probably accuse you of overstepping your boundaries or whatever. I'm NOT saying that I think you are, I'm saying SHE will probably think so.
To head it off a little, I'd be having a conversation with the mother, even if its brief and to-the-point, about the questions she is asking and about how you are answering them (being respectful of her beliefs, etc.) and I'd tell my husband, too, in case the ex-wife gets all mad at him for it.
And don't put too much stock in what the child is saying about her mother, either, unless you have witnessed what she is saying first-hand. Children of divorce are very, very good at playing both ends against the middle, trying for every advantage they can from the situation. I'm not accusing her of lying or being a bad kid, I'm just talking about the tendency of ANY child is to try to take advantage (they do it in natural families all the time, too!) A child of divorce is likely to play up to the sympathies of the family they are with, so watch out what she might be saying about you to her mother! Which is why I'm kind of warning you to tread lightly. She could be truly curious about all of this stuff, or she might be laying a trap for you (consciously or unconsciously) or being put up to it by her mother!
I do not discipline my stepson myself, and questions of that sort are things I say something along the lines of, "That's a question for your father" which is handy for me cause my stepson is a boy. In your situation, I'd say something like, "What does your mother say about it?" or "What WOULD your mother say about it? Should we ask her together?" Lastly, I would say something like, "This is what I think, but you should also ask your mother or father." However you do it, make sure you are letting her know that you are respecting her natural parent's beliefs on a certain subject so that no one can lay a trap for you.
Sorry for such negative advice, but I've been there, and again, I'd say tread lightly.
L.