Damn brother, that's rough. I'd just say, it depends on how much you love her and if you're willing to forgive her this one time. 11 months is a pretty good amount of time to be together. For some people, cheating is the only thing they won't tolerate. "One strike and you're out" kind of deal. Others can forgive a one-time incident. I think you have good advice from the others to think it over for a bit and tell her you need some time to process it. You may feel differently after the hurt dies down. It just depends on if you see yourself with her after that happens.
Good luck, man and sorry to hear about it. I know I don't know you, but regardless, being cheated on sucks from personal experience.
It'll be awhile before I figure out how to do one of these. :P
