It's always tough to make an accurate assessment of what's going on with someone based on secondhand information, and behavior like what you're describing could come from any number of places. Best case scenario, if she's naturally small and has never had a problem with her weight, she could legitimately (if erroneously) see you as heavy and be reacting out of tactless but genuine concern. Worst case scenario, we're looking at someone with an undiagnosed eating disorder, body dysmorphia, and/or a personality disorder, any of which could result in distorted body image, rigidity of thinking, and excessive criticism. Or any number of points on the spectrum in between. Without knowing more about her and your relationship with her, I couldn't say with any certainty. But the 'why' is really far less important than what you do about it.
I'm a firm believer in the axiom that hell is other people. You wouldn't believe the number of people I deal with on a day-to-day basis - both professionally and personally - who are massively unhappy because one or more people in their lives just won't behave the way they want them to. The simple fact is that you cannot change someone else's behavior. You cannot do it, and trying is as futile and painful as banging your head against a brick wall. What you CAN change is your own response to other people's behavior.
The situation with your mother is a prime example of this. She's doing something that bothers you, and she's persistently doing something that bothers you. So it falls to you to start setting some limits. Begin by explaining to her in a clear, calm, and concise way that you find her comments hurtful, that your weight is no one's business but your own and your doctor's, that you'd prefer not to have that conversation with her anymore, and pretty much that you're not willing to listen to it anymore. And then comes the tough part. You stick to it. When she tries to push back, you don't let her. She brings it up, you remind her what you said before and change the subject. She continues badgering, you end the conversation or excuse yourself. Ultimately this may mean having less contact with her, which is tough, but worth it to avoid that negativity. And ultimately, one of two things will happen. She'll get the hint and give up, or you'll get exceptionally good at putting the kibosh on it. Either way, you'll find yourself having to listen to it a lot less.
First question
I'm a firm believer in the axiom that hell is other people. You wouldn't believe the number of people I deal with on a day-to-day basis - both professionally and personally - who are massively unhappy because one or more people in their lives just won't behave the way they want them to. The simple fact is that you cannot change someone else's behavior. You cannot do it, and trying is as futile and painful as banging your head against a brick wall. What you CAN change is your own response to other people's behavior.
The situation with your mother is a prime example of this. She's doing something that bothers you, and she's persistently doing something that bothers you. So it falls to you to start setting some limits. Begin by explaining to her in a clear, calm, and concise way that you find her comments hurtful, that your weight is no one's business but your own and your doctor's, that you'd prefer not to have that conversation with her anymore, and pretty much that you're not willing to listen to it anymore. And then comes the tough part. You stick to it. When she tries to push back, you don't let her. She brings it up, you remind her what you said before and change the subject. She continues badgering, you end the conversation or excuse yourself. Ultimately this may mean having less contact with her, which is tough, but worth it to avoid that negativity. And ultimately, one of two things will happen. She'll get the hint and give up, or you'll get exceptionally good at putting the kibosh on it. Either way, you'll find yourself having to listen to it a lot less.