What should I do with my overly caring personality?

My girlfriend and I have been together for almost 5 months now, and we both love each other inexplicably much; but I am in loss of what to do with my over caring personality. This summer I have to be away from her, and lately I’ve been noticing a change in my patience and altitude towards things; I care about her more than anything, and things like other guys hitting on her have always bothered me, but lately I can’t keep my mouth shut and act as if it doesn’t bother me much. On multiple occasions she’s told me she was getting “unwanted” attention in public. Her boss is overly nice to her, he’s always been treating her better than all the other employees; he even purchased her a birthday cake. On other occasions he has given her compliments such as that she is attractive, and that he has a soft side for her because she has a very sweet smile. In my opinion, this kind of behavior is unprofessional, especially towards a minor. What bothers me the most is her response, she’s told me that all his little compliments melted her heart and that he is very sweet. Today I lost it and told her that I’m uncomfortable with him acting this way towards her, and her being so okay with it. She didn’t see why I was so concerned. I told her to keep all the stuff between her and her boss, as I did not want to hear any more of that. I always pay lots of attention to her; so this isn’t her hinting towards me not being affectionate enough. She sees this relationship being very serious, and always tells me she wants to marry me etc. I don’t know what to do, should I just stop caring as much about her and the relationship in general? Should I just brush things like that off and stay quiet? That sounds harsh, but if me caring is frustrating her, what am I left with to do?