Calling all Carrie Underwood fans! I need your help.?

It's something about some guy that she loves is getting married or something(idk)- anyways, she can't be with him for some reason. When I was in drivers' ed, the only thing that we listened to was country music and my law ed teacher only plays country music, but I haven't heard this song in a long time and it's been bugging me since I can't remember it. Can anybody help me out based on my meager explanation of the song, plessse!