Why is my friend jealous im flirting with a guy she doesn't like?

My friend has a couple of guy friends. They flirt with her and she might flirt back but she doesn't necessarily want them. They flirt with me as well but when they do she comes over and tries to be the center of attention. there's one guy that flirts with me and we hang out together and she gets jealous about it. She blows his phone up when him and I are together but she doesn't like him.

Why is my friend jealous im flirting with a guy she doesn't like?
Post Opinion