I fucking hate rude people. How can I respond/react?

Alright guys, this girl is starting to get on my freaking nerves. I take summer precal with my best friend (guy). He helps me with things i need & sometimes when I’m getting help, she’ll interrupt and ask for help with things she needs. It’s gotten to the point where I’ll go ask someone else for help instead and he gets mad because he was helping me but I’ll go get help elsewhere. HOWEVER it’s his fault because he doesn’t tell her “wait” or anything, he’ll go and help her in between. Not only that, when we get our test results back and I’m comparing answers to see where I went wrong or he did, she’ll tell him “let me see your test” & try to get it out my hand clearly knowing that I’m seeing it. I’m at my wits ends and if someone doesn’t put this girl in her place, I will.