Is it normal i emulated finger sex with a girl in class and she responded by...

So I was sitting next to this girl in film class at the university and I had noticed how sexy she looked sitting there arching her back, heaving them out, and the way the chair brought out the shape of her lower torso so well. It got me excited thinking about her and as the movie came on, (we were in a film history class together) I began emulating stroking her softly but effectively with my fingers in a way so that she alone was privy to what I was doing. I was one seat over and a little ahead of her desk. What got me really hot, was that she started doing the same thing in response with her fingers, suggesting a sensual hand massage! It was rigid bliss for about an hour until I realized I would have to get up and face her and everyone else when the lights came on. I chilled out, and we never said a word to one another about it! Does this happen to you too?