Falling in love in a dream?

Okay, first of all, hello everyone, this is my first post here and here's what this is about:

A couple of months ago (only decided to ask now =P) I had a strange dream where I fell in love with the twin sister of a friend of mine, which I've barely spoke with since I met her.
Okay, where does this gets weird? During the day after I had the dream the feelings endured. It's like, one day she means nothing, and the other I'm completely in love with her. Like really, it even made me feel bad with myself. It faded about one or two days later and I'm back to normal now, but still... It was really strange to me, specially because I have a girlfriend and I do love her very much.

All I wanted to hear is your thoughts about that, since it got me a bit worried and know if anyone has experienced that.
Thank you!

Maybe its cause of hormones or cause you were thinking about it for a bit. In dreams your mood can be influenced to make you think something is true at times too. An example I experienced is seeing a place I feel I've been to but I haven't ever been there before