<human>: So he has asked me if he has the right to be upset and if it is worth bringing anything up with his GF.

First thing is, she was playing on her phone with him and he managed to see a missed call from her ex boyfriend, which he saw that she had called him back and spoke to him for 5 minutes.

Second, she went out with some of her girlfriends on the weekend (she tends to get very drunk) and one of her friends was getting hit on by a guy at the club. The guy was there with his male friends and invited them all back to his apartment. So his girlfriend and her friends went back to this guys apartment at the end of the night and we don't know what happened as he didn't really interrogate as he didn't want to come of as overprotective or that he doesn't trust her. 

Third, (He thinks that she already doesn't make too much of an effort and can be selfish). She is away for the week on a holiday with her girlfriends, and told him she was going to call him before bed but she ended up texting him saying she just started something (a game i think) with the girls and isn't going to call. (I know its small but it's adding up on him).

He claims he trusts her and shouldn't be worried but he wants to know if he is overreacting or has reason to be angry?

I have told him ultimately if you trust her none of this should matter but I also believe he has a right to be upset.

What do you all think?

Can you succinctly summarize the text in 1-3 sentences?
<bot>: My mates girlfriend has been texting her ex bf, going to random guys apartments with her gf and not calling him when she said she would. What advice do I give him?