Is she a good friend?

No shes definitely NOT a good friend. She swears but that's okay and as long as she doesn't constantly swear at you its okay. If shes getting in moods it might just be mood swings but taking sides is just really pathetic if shes not involved, then shes just trying to be the centre of attention and get involved with other peoples arguments. If she makes fun of you, maybe its only a joke but if she takes it too far just tell her not to or the next time she does something stupid just make fun of her back then she'll know what you feel like when she does it to you. If she doesn't like your other friend tell her not to sl'ag her off or get in a mood about it, just tell her shes being spiteful and jealous and to get over it, tell her shes not your only friend and that you can be friends with whoever you want to be whether she likes it or not. If shes being a b'itch to you about you doing something good and isn't being supportive and happy for you, whats gonna happen in 5 years time when you get an amazing boyfriend? shes just gonna be like wtf i don't care and not help you when things get rough. At the end of the day if shes not willing to be supportive and make an effort to keep you as her friend then she doesn't deserve you, you should just tell her to do one and hang around with other mates. Hope that helped :) x