I know where you're coming from, but you have to stop thinking that way. You're not a mind reader, and you can't act like you know what people think of you. You'll just end up driving yourself crazy.
I recently had an experience at a movie theater where a man and his wife made fun of my weight. At first, I hated myself and I thought that EVERYONE felt the same way.. but then I remembered that.. if it wasn't me there, they probably would of made fun of the person in my place. People like that, like the two girls you ran into, they don't care if you're fat, skinny, tall, short.. They will find something wrong with you and they will poke fun at it. Remember that, and you will see how full of bull**** they really are.