These girls gossip about EVERYONE? help?

Hi, I'm 14, freshman in highschool. These two girls that sit behind me gossip about everyone,and they think they're better than everyone else. They think they're so nice and stuff, but they're not. They're like "oh Hanna is so rude., ikr. She needs to lose weight." And that kind of stuff. And they're rude too. I introduced myself to them on first day of school, and they're like "whatever". And ignore me.
They're so rude. What do I do? And I heard them gossiping about my ex boyfriend, and yeah I said something to them because I still have feelings for my ex boyfriend, even though he cheated on me.
Why do these chicks gossip about everyone? During english they gossiped about every girl there is to know at the school, and if I counted corectly they said stuff about each girl, and there were 30 girls they mentioned.