She's ruining my NSV's!!! (Or, I'm just an ungrateful b*tch...)

Remember that look your mom threw your way when you said something infront of an adult you shouldn't have?  She remembers that look also and you can mimic that. 

 You can also tell her that you want to be the one who tells what you have accomplished.  I grew up in a family where my sister and SIL always told my news to everyone before I had a chance.  It was degrading to me and I hated it but because I was the youngest, I never faced them with it.   Don't be afraid to speak out, it might improve your relationship more then you know.

 "But PLEASE stop telling everyone I used to be a big fat pig......"

The first thought that came to my head when I read this was "If she met me, would she think I was a big fat pig? Ouch."  

I am very private about my weight loss, too.  Other than ObesityHelp, my mother and my boyfriend, I do not share my personal struggles with anyone.  I have asked my mother and my boyfriend to support me in trying to be who I am today, not keep reminding me who I was yesterday.  They have both responded with being super supportive.  I am guessing if approached right, your sister would be the same.

 I am having this problem with my mom. Every-time we do anything from going out to eat to shopping to just chatting with random people, she tells them. "She just had that gastric surgery and lost a bunch of weight" it's embarrassing as then they want to ask a ton of questions and I usually get at least one person who says "oh" like my weight loss is not as good since I had surgery. 

I've tried to talk to her about it, but she just says, well I am proud of you. I know it's frustrating for sure! You may just have to sit down with her and explain how it makes you feel and that you would like to keep that part private from the rest of the world.