His girlfriend went to the gym for fitness, and he added WeChat. The coach taught her for free, saying that he would be fine after two classes.
It's hard to say. First of all, you need to know whether your girlfriend is the kind of person who will cheat, or you can talk to your girlfriend about this problem. Don't say that you think there is something wrong with your girlfriend, just say that you think the coach has ulterior motives. Tell her to change coaches and see how your girlfriend reacts.