My mother did the same to me. I didn't have a completely unhealthy relationship with her though, I used to look up to her for a lot of things. She can be very good at times and other times really down the hill.. so her making fun impacted me all the more, starting from the age of ~12 when I started stuttering. I sometimes feel if she hadn't done that maybe I wouldn't be still nervous and stutter. The stammering is a lot less now ( I'm 35 now), but the pain/memories from childhood is still there. Advice if I can give you would be to be open with her and tell her to not do that to you, be strong in that conversation. And then make distance if you need to, but maybe the confrontation could help your inner confidence !