Andrewj3206 you might want to tell your friend to stop lying to you. This song was written by Katy Perry. I'm seriously looking at the cd insert right now. I'm sure if your friend actually wrote the songs that you mentioned she or he would be rollin' in the money.
As for the song meaning, it's pretty much self explanatory. She loves one man, but is unfortunately stuck with the other. She also isn't able to be with the man she loves. In the video, it was because he had died at war.