No, not a native English speaker.
I would also be fine if it was just HC was disappointed in her performance. BIG difference. So I'm not saying anything right now.
I think you are making the right decision then. Look at this in the big picture. If most things are positive in the gym, this could have been a misunderstanding on your gymmie's behalf, a language error on the coach's behalf, or a coach in a bad mood making an honest mistake.
Now if it becomes a pattern, that's another story.