My friend is mad at me?

I think that you should make sure that she knew that you didn't mean any harm by hanging out with him, you guys were just talking. I think that she needs to loosen up but I still think you should apologize (even though we both know you did nothing wrong, you want your friend back). Ask her what's going on. There might be something going on at home that's influencing her to be so impatient. Hope that I helped and good luck with your friend :)