I know the withdraw attention method when I see undesired behaviour. But sometimes I feel like I need to address the problem.

For example last night we had a social event and she touched my friend's body (and once in the leg close to the dick) after he said he got punched. She wasn't showing any affections or flirtations, we also had one or 2 drinks)

I treated very carefully so when we got back to her dorm I told her I don't like my girlfriend being touchy with other guys as it ruins my image. She said she's sorry she didn't see them as "guys" just people.

How did I treat the situation? Could I have treated this situation in a better way? I don't want to end it just yet as no major red flags have shown so far.