Is it normal to be annoyed by this?

I was hanging out with this girl for the past couple hours and we were just walking around town and having fun. I haven't known her long at all and she's a freshman at my college and I'm a senior so I was showing her around town and just goofing off.

Anyways she mentioned it was getting late and she has class early tomarrow so I took her back to her dorm, as we got to her dorm just before I left to go to my dorm, she said she got a text from a friend she was going to go hang out with, she offered me the chance to come along but I declined and wen't back to my dorm.

I know I don't have any right to be annoyed by this but it upset me some that she decided to go hang out with another friend, when she had already decided to go to sleep instead of continuing to hang out with me. I know it's petty but it annoyed me IIN?