Maybe my first girlfriend a little, the main issue was the lying and hypocrisy (she would get jealous at nothing, but was eventually shown to be the cheater herself). That was 10 years ago though. You are setting yourself up for more damage if you are too jealous/territorial or whatever you want to call it. If you didn't put a ring on her finger, then you have to watch out whether you are really in a mutually exclusive relationship or not. Most of the time it is just understood that the relationship is mutually exclusive and it is never fully expressed until someone gets jealous. Really the torture you put yourself over being territorial or jealous over a mere friendship is trivial at best (suspecting cheating depends on the person's past with you). That being said it is really difficult to avoid getting jealous/territorial when you are in love.
