Why is my friend so toxic? And why does she always put me down?

She's not a friend. She's a bully. It's that simple. No real friend would put their friend down like that. Honestly, she does seem like a stuck up female dog. I really think that you should stand up to her. You shouldn't let her walk all over you like that. I know you don't want to be rude or anything because you seem like a sweetheart to put up with all her crap. But I really think that you should tell her that you don't appreciate how she's treating you. If she's willing to change, give her another chance. If she's not. You can and will find better friends.