Sounds like your mother cut ties with her own mother or relatives. Too bad she doesn't wish to share her previous life with you and doesn't remember much of your young one.

If you still live with your mother and she needs money for you all to survive, I can imagine her stealing from your funds. My family was relatively "well off" when I was growing up but had 5 children and my stepmother told me she borrowed from my savings account sometimes when she needed money (but claimed to pay it back). I didn't know anything about it until my high school girlfriend and her mother were laughing at my naivety, thinking it was for my "safety" having my mother's name on my savings account in case something happened to me so they could get the money out.

Hope you get to a place where you and your mother have better communication and understanding of one another.