Well, they should do that another way: they should ask Misty, and if Misty would be asked, she'd refuse, so then isntead of forcing Misty, they should just appoint a replacement. And they wanted one holiday, not traveling like Misty.
Indeed, forcing Misty without giving her a choice is what makes this worse: they screwed Misty over, and now her life is ruined. They should've just given her a chance to refuse, then they should've appointed someone else. I'm sure Dorian (Johto character of the day) would've been a good choice: he's a very good Water Pokemon trainer, he wants an official Water Gym, he'd be perfect.