<human>: Can you give me the gist of the text in a nutshell?

I'm an exchange student and I've been having a really difficult time adjusting and making friends here, this girl is one of my only friends. I often talk to her brother and joke around with him and she didn't seem to care, but last weekend him and I kind of hooked up. We made out and did like "foreplay" but not actual sex. And she found out. I don't know if he told her or how she finds out, but she's confronted me about it this morning, and I denied it and I was really nervous and she pretty much said she knows I'm lying. She seems really pissed at me and I didn't intend to make her angry or anything but is she over reacting? I think she is overly protective of him. I know it's kind of bad to hook up with your friend's brother but I don't have many friends here and I wanted just to be friends with him too. I don't have a boyfriend or very much friends and I feel really alone. Should I admit to her that I did it or no?
<bot>: My friend is mad at me for making out with her brother, she accused me of it and I denied it but she didn't believe me and I'm intimidated by her.