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

Sounds like shes just growing out of you (sorry). Shes jsut going thru that phase of being a bossy know-it-all. And if shes treating you like that maybe you should forget about her.. I had a friend just like this and her mom made her invite me to everything cuz she just didnt like me anymore. You can either forget about her or talk to her about it.