Help, my g/f is trying to break up over a bodily function?

Last night, I let one while we were sitting on the couch watching a movie. The air conditioning was turned up, so it was kind of cold and I had a blanket wrapped over us and I took the blanket and pulled it over her head so she could smell it. I did it just playing around, but after she got the blanket off her head, her face was red and she was very angry. She just stormed out and never came back. It has been 24 hours since the incident and I still haven't heard from her (accept for a text message saying she is breaking up) and I don't know what to do. I don't know why she is over reacting to this.