Pointless Griping

Yes, highly inappropriate and you should not let her go without you- better yet, make an excuse and don’t go at all - that way you avoid conflict.
Group sessions like that will always kill the beginners and are worse if a meet is near. Treat the session just like a tough meet with rounds and do all the therapy you’d do then, hot/cold showers, massage, etc, and stick with tempo for a week.