I totally understand. You might google maternal transference. Please please bring this up with your T! It seems incredibly hard but it's helpful for them to see the entire picture. As my T. said, she has a lot of puzzle pieces trying to figure me out. If I don't tell her things or think they aren't important, I'm throwing out some of the puzzle pieces she needs and they might be end or corner pieces.
She will completely understand and probably already knows it. I would also suggest asking an older lady (maybe some you already feel comfortable with) to, you could phrase it, be a "mentor" to you.
And, once you tell your T, she will have all sorts of ways to help you. From suggesting how to get what you need out of sessions to helping you deal with it right now.