Set boundaries. Stop seeing her if it's all she talks about.
Basically this. Speak up. Tell her that her staring at you and her comments are really upsetting. She'll start spouting off excuses. Stop her and tell her that you know you've gained weight. You don't need her reminding you. And if she can't stop staring or making comments, you're going to stop spending time with her.
And then - do it. She doesn't stop, stop seeing her.
Your mother's behavior sounds offensive, so I don't blame you.
How would she react if you told her you didn't want to discuss clothes/weight/appearance?
She would give a sarcastic apology and then she'd start telling everyone how crazy I am.
Don't give her more power than necessary - do you really think that the people she tells that you're crazy believe her?? No, they don't. Don't worry about what she says.
Distance yourself. not forever. But make it clear that you aren't going to put up with it. You don't enjoy spending time with her. TELL her this and then stop spending time with her. At least for now, to get the message across.
Set boundaries. Stop seeing her if it's all she talks about.
Basically this. Speak up. Tell her that her staring at you and her comments are really upsetting. She'll start spouting off excuses. Stop her and tell her that you know you've gained weight. You don't need her reminding you. And if she can't stop staring or making comments, you're going to stop spending time with her.
And then - do it. She doesn't stop, stop seeing her.
Get an index card and keep it in your pocket that says "You're staring at me."
Hold it up every times she stares. Smile.
Don't think that she doesn't KNOW she is doing this. Of course she knows. It's giving her a thrill or a sense of power or satisfaction. Stop it. Stop allowing it.