Oy. She's young, immature, high maintenance, and the whole thing seems like one hot mess.
In addition, I think your reactions and some of your statements don't really sound like you would actually be okay with her having other relationships. It sounds like you really wouldn't be happy in a poly situation with her.
It will hurt for a while, but it seems the best thing for you right now is to walk away. I say dump her and move on.
The world opens up... when you do.
"Oh, oh, can't you see? Love is the drug for me." ~Bryan Ferry
"Love and the self are one . . ." ~Leo Buscaglia "