What do you do

When your boyfriends flatmates (a boyfriend and girlfriend) boss him around, like tell him he needs to meet their friends etc. He just left my flat because the girl wanted him to say goodbye to her friend who was visiting. He was ignoring her texts at first but then she started messaging and calling me to tell me she's trying to get hold of my boyfriend (so that he can leave mine). I'm so upset that he's left.

Please don't tell me to break up with him, I love him. I just want him to realise.