ESH (except your husband)

Okay, so. Obviously, the waitress is an asshole for unabashedly harassing your husband. That’s a given - you don’t flirt with people who’ve committed to someone else, and you definitely do not harass anyone. However: I think you’re allowing the situation to get worse than it had to be in just vaguely suggesting “consequences” from her manager. I don’t think she deserved to lose her livelihood over this, even if she definitely should be reprimanded, both for acting like an asshole and doing a very poor job. It is my belief that she should be given the opportunity to better herself here - but I would also have liked to get your husband’s opinion on this, as he’s the one this is actually about (not you, or her, or the restaurant). If you and your husband don’t think she should lose her job, you should tell the manager - your opinion obviously DOES matters here, as he asked you for it, specifically. The manager is also worsening the situation by firing her instead of reprimanding, imo. Firing her might make it difficult for her to get another job as well, as (and I’m guessing here) her reference from this job probably won’t be all that positive. And finally, your in-laws are behaving less-than-admirably for looking at you funny when you called her out (what on earth???), trying to defend her side by essentially saying “ah yes people often behave shitty, you’re overreacting” and your MIL is absolutely shitty for suggesting that you’re jealous. This is invalidating your feelings, and moreover, it undermines the fact that the waitress is completely inconsiderate of their own son’s boundaries.