Is my girlfriend cheating on me? She does this with a guy

Is my girlfriend cheating on me? She does this with a guyFrom a male blog reader:

Good day, kindly advice on what to do. I have been in a relationship with my girlfriend for over four years. Out of which we have had very serious issues especially trust which could be traced back to both of us. She recently finished her service in a far away state. During her service year, much of our issues are mostly trust related. On her part, at the beginning of her service year, she stayed together with other Corp member at a family house. I started by complaining about a particular guy in the family house who I don’t like the level of closeness but fortunately the guy moved out of the house. My girl also made attempt to leave the house too and unfortunately, according to her, she unknowingly got a room in the same compound with the same guy. I was furious about the whole thing but I summoned up courage that the service was just for one year. While they stayed in the same compound together with other lady corpers, they all cook together nd mostly stay in each others room. I complained that I don’t want my girl hanging too much around the said guy but she never stopped. She told me nothing was between the both of them which I believed or let me say tried to believe. They were so close to the extent that the said guy can enter my girl’s room at any time without even knocking, take pictures bare chest in my girl’s room and even post such pictures on instagram. At every point I raise objections to these my girl will flare up and act defensive claiming I need to be able to trust her. Now, her service year is over and she got a job interview in the state where she served. The matter now is I don’t want to continue having the same problem I had all through her service year and on the other hand I can’t stop her from taking up a job since I don’t have one waiting for her here at home. Please kindly advise on what to do because I love my girl so much and I don’t want to lose her.‎