If so why are you jealous let's say someone is making new friends and you feel left out all you need to do is talk to your friend.
For instance you are new and have no friends all you have to do is go to someone that looks nice and ask to play with them or hang out with them.
Let's say the "cool girl" has beautiful clothes you don't and she makes fun of you just say "ya know what you can be mean but don't think it makes people like you! Because it doesn't! It makes people dislike you so just stop ok!" Then walk way.