Why did this random girl give me an attitude?

I'm starting college this year. I went down there to take care of some things and I needed some information about where things were located on campus. I went to the information desk to ask, there were two girls there. I asked the one girl where I needed to go and she began to tell me, then all of the sudden the girl who was standing behind her that I wasn't even talking to ed in with a very loud and condescending tone and told me where to go. she just cut the other girl off that I was talking to. Why would this girl be so rude if I wasn't even talking to her, was she mad that I wasn't giving her attention I don't understand.