Does she make you go to church or something?
If not then I don't know why you can't let her think you're Christian. She may think that if you're not Christian that she'll be without you for eternity while you'll suffer eternally and that's not a thought she can stand, so it might be kinder to just let her think you're "saved" if it's not too much trouble.
Of course if you gotta "be you" and make sure she knows it then just try to think which is more annoying: nodding whenever she praises Jesus or quotes the Bible (maybe you could make a game of it, like with your own bingo cards of her favorite verses and Biblical names/books, and bonus points for not sighing or rolling your eyes! :tongue: ), or her trying to convert you back, and pick the lesser evil. (Note, if you're in the US then she can legally have you abducted and put into an abusive Christian home--possibly in another country--to brainwash you, and they can make you believe, I had a friend who was brainwashed by one when she was 16 who came out believing I was in a satanic cult. You'll probably say your mom would never do that, but thing is most parents have no idea how abusive these places are, and you should also ask yourself, would she let you burn eternally when that possibility is all too real to her?)
If she does insist on church attendance you might try going to a
UU church. Some Christians are fine with this (and your mom being ok with you being gay is a good sign that she's one who would accept this) while others are not (Texas even tried to have the UUs revoked as an official religion at the state level). They include different religions (including Christians, but also Hindus and even Wiccans) so they don't seem to spend a lot of time on religion but rather some broad ideas about God/dess that should be much easier for an agnostic to put up with (as an added bonus they're officially gay friendly).