How to handle this...

So my mom & I don’t have the best relationship. She constantly let her friends & other family members body shame me growing up & even partook herself. She was always making comments about my body & telling other people. I remember distinctly being 9 years old & starting my period - she had to call everyone & tell them. Not long after I developed breasts & obviously needed bras. We would see someone she knew & say things like “did you see she got boobs now?” or “I had to take her shopping because she got boobs & needed bras”.

Well, my oldest niece is 11 & a LOT like me, both in size & being an early bloomer. My mom is starting to do the same thing to her. My niece was playing in the pool with her bathing suit on (obviously) & my mom kept going “can’t believe she’s old enough to have boobs” or “when did ___ get boobs?”

It makes my sister & I very uncomfortable & we’re not quite sure how to handle it. I told my sister mom did that to me as a kid but my sister said she doesn’t remember our mom doing it to her.