However, I did notice later in the evening when my stepbrother and his wife came over and introduced me to my new niece (she is so lovely!), that my mother was talking about myself and my brother as babies, and effortlessly getting the pronouns right.
We'd planned to spend the night and leave the next morning. I felt too rough to leave straight away after a restless night, and ended up having a bath there. While I was in the bath, my mother walked into the bathroom and, for the first time, saw me naked with a female body. She didn't miss a beat.
I think she's really accepted, and got used to, the idea that she has a daughter. It feels good.