Is it normal that i think have feelings for a female friend?

Okay, so I have been friends with a girl for years now. I am a bisexual girl and until now I've never had any feelings for a female friend at all. However we attended a concert a few weeks ago and I was suddenly struck by how pretty she was in her excitement and felt a little jolt in my chest as she was dancing.

Is it normal that I feel that way? Was it a spur of the moment thing that was maybe brought on by my adrenaline rush at the concert? Or is it something more and should I be wary of this?