Uhm you can maybe do she moved from her old school because her dad and her mom got a divorce and she starts to fall for the school nerd/bad boy (same person) but the mean girl is dating him (like actually dating) And then the boy becomes friends with the MC and he starts to like her and tell her everything so with that he tells her that he is only dating the other girl because they were childhood friends and at some point he breaks up with her and then her Ex come in and he is jealous so her ex and the nerd/bad boy´s ex start dating to make the other two jealous and the boy actually gets jealous so he goes back with his ex but the girl doesn´t go back to her ex… and now I don´t know anything else… 
But if you want I can think of something else and PM you after I´ve thought of it?