Backstory: before becoming pregnant I was told I couldn't have kids because of my anorexia and bulimia but a somehow still became pregnant. My SIL (16) has anorexia as well and was told today that her liver is eating itself. 
So tonight at dinner my MIL was trying to scare my SIL into eating by saying "you don't want to have the same thing happen to you that happened to tylynn, you know that's why she had Ashton so early. She hurt her body so it hurt her back" like what the actual fuck? She was there when I asked my Dr if that was why I had him so early and he said no. And the worst part is she's said stuff like this before and thinks it's okay. Well this time I told H cause I didn't know what to do so he talked to her and she then texted me in a group message with him apologizing to me. I feel like she only apologized to me to make sure he knew she did. Now my H is mad cause I won't text her back. My question is how can I talk to her to get her to understand that she can't just say whatever she wants to me? And how would you handle the situation?                
                Married 8/9/13
Ashton James Rogers 10/29/13
              
        
Re: What should I do? (Vent)
PCOS diagnosed secondary infertility
BFP #1 (letrozole 2.5mg + ovidrel) February 2016, MMC April 2016 @ 7 weeks
BFP #2 (letrozole 5mg + ovidrel) July 2016, Beta #1 359, Beta #2 745, Beta #3 11484
EDD April 9th, 2017
partial molar pregnancy : bfp 6.28.10, d/c 8.17.10, 7 rounds methotrexate, cleared 7.1.11
alexander patrick : bfp 1.16.12, born 9.20.12 @ 39w1d, 7 lbs./11 oz./22 in.
scarlett irene elizabeth : bfp 5.24.13, born 2.3.14 @ 41w2d, 7 lbs./13 oz./19 in.
BFP 11.8.12 * EDD 7.17.13 * MC 12.20.12
This is what really gets me about this. She knew how you felt and she knew that wasn't why your son was born early. If she was trying to make it up to scare SIL into her senses, she could have said it when you weren't around since she should know how it would make you feel. Still shouldn't say that even then tho... And if she still believes that is the case after hearing your doctor say the two weren't related then she's an idiot. I'm so sorry. She's a total bitch.
First of all, your MIL has no right to say the things she said or making you or your son as an example to your SIL in order to scare her into eating. That is the most hurtful thing anyone can say! Besides, scare tactics do not work for people struggling with ED. Like the PP said, your MIL owes you a personal apology not one via group text message. If you do decide to sit down with her to talk to her about your ED and how her comments affect you, my advice is not to have high expectations. My friend had to have several conversations not only with her own Mom, but a coworker that we also consider our "other Mom." It came to a point where she had to stand up for herself and set her boundaries, not just for herself, but also setting an example for her daughter to show her that her feelings do matter. I've found that people of older generations do not understand EDs because they think EDs aren't a real disease and it's simply attention seeking. And no matter how many times you talk to them they just don't get it.
I hope that however you decide to handle your MIL you do it for yourself and no one else. Also, I hope that your SIL continues to seek help for her ED and she overcomes this. Good luck to you both!
She needs to find another way to scare your SIL.
Totally inexcusable.