How do you deal with unsupportive friends/family?

Honestly? You're probably not going to change her mind about food. A lot of people associate gatherings and food, food being something that brings people together. If she asks you what you want for dinner when you go over there, give her some options and enjoy what she makes. You may have to do some adjusting to fit it into your calories for the day, but if you limit your portions, you should be ok.

Only suggestion I have is to be firm with your choices. You might also try inviting her over to your house and cooking for her. If she sees that what you're eating is fairly normal, she might back down some.

This is a bit of a head scratcher. I'm not sure why this is so upsetting.

Your MIL thinks you are vegan. How is that hurting you?

You visit your MIL and she asks you what you'd like for dinner. How is that hurting you?

I completely understand where your coming from!!!! I've been eating healthier for about three weeks now and I live with my boyfriend at his mothers house. She is already a two-faced drama starting person that I don't like, but on top of that she orders out all the time...as soon as I decide to eat healthier and portion my food she has to start making comments about me " carrying around measuring cups". I don't understand why it's such a big deal that she has to make comments about it, we buy all our own food so it's not like I'm making things difficult for her. I just can't stand it because people like her are the reason so many of us get discouraged from trying to be healthier in the first place. So hakuna matata and keep your head up

Smile your best daughter in law smile, say "thank you so much for respecting our choices!" And then shut up. And then tell your husband to grow a pair and deal with his own mother.

I'm not sure that I understand why you are so upset.

My mother and my MIL like to have us over and always ask what we would like to eat. They are from an era where being a good host meant feeding people (and many times, this is still tradition). It's no big deal. And I always offer to bring something that I know I can eat (like a salad, or a side, or especially a dessert). Maybe next time offer to have her over for dinner, or suggest a dish that you can provide? When someone makes something that is questionable with my macros, I just pick and choose what I can eat from what is available.

About the vegan thing. I wonder if she is mixing it up with something else in her mind.

You cannot talk to her about these things. She is not going to listen. Distance yourself as much as possible.
Certainly make your husband do the talking if anyone has to talk.

Luckily you don't live with her. On the rare occasions you do eat at her house think of something she makes that isn't too bad and ask for that. ( roast chicken or turkey?) My MIL knows my daughter had a gall bladder attack and is on a strict low fat diet until she can have it removed. I saw her put an entire stick of butter on top of the eggs when we went there for breakfast. Then she wondered why my daughter did not eat the eggs.

you broke rule #1 - don't argue with your inlaws, that is for blood only

if you ignore her long enough, she will get the point.... its been about 5 years and I still have to ignore my father in law.

"THIS IS A TEXAS MEAT EATIN' HOUSE, NOT THAT GAY CALIFORNIA PLANT STUFF"

im from LA and I have yet to hear the end of it- even tho he begrudgingly admits he likes my cooking and he take 10 medications for heath related conditions....

stay strong and ignore, let your spouse scream at his/her own mom

Maybe she is like my mom, who feels intimidated by "different" diets even though she wants to be supportive. She doesn't get it sometimes. For example we eat her homemade baked goods, knowing that she is a user of skim milk and Splenda/sugar blend and so on...but when she brings out a frozen aisle apple pie with 500 calories per slice and sky high sodium we usually pass, or split a piece. It doesn't make sense to her. And that's ok, really. It would be a lot to expect of her to always have our favorite foods on hand and eat exactly as we do. She's never gonna enjoy plain Greek yogurt with chopped up fruit and oats in it as much as her McDonald's yogurt parfait.

When she asks "what do you want to eat?" we usually ask her to make something we know is "innocent". We go to her place weekly for dinner and we often bring restaurant food of our choosing (which she likes everything so that works) and if she "cooks" more than 50% of the time we have large, loaded baked potatoes and my husband (who is pescetarian) brings his substitution for taco meat (TVP) and we bring a container of French onion dip we love, and leave her to the Velveeta cheese sauce and bacon pieces she prefers. We all eat broccoli on our potatoes and I'm fine with her low sodium taco meat...so everyone's happy. But if we told her "whatever you want to make" we would be eating boxed and canned food only, and a lot of things we didn't prefer to eat like Frito chili pies and boxed entrees with off the charts sodium and fat and so on.