I Was Thinking About Something

I have always felt i was too skinny my whole life. I wanted to gain wait a few years ago and now its happening without me even trying. Im 5,3 at 121lbs. I was starting to feel better about the way i look since i dont feel i look too skinny. Then my sister says to me " you're getting fat".
This is the first time someone has EVER called me fat. Made me feel bad. i usually get " ew, shes so skinny, she looks sick, anorexic". Just goes to show, people are gonna talk about you no matter what. First i was TOO skinny and now im fat?...