Dinner date didn't go as expected

This is a short horror story, but I still shake my head about it. Not sure it fits the "SA" trigger warning, but it contains inappropriate behavior at minimum.

Many years ago, I was very interested in RPG but only had played one session before. So I was very excited when I got an opportunity to play again:

My bf at the time was playing a campaign with some of his friends online. His character had a love interest in the campaign, which was an NPC. When I got to know his friends, the DM had the great idea to invite me to one of the sessions and let me play said NPC for one session. For reference: I (f) was around 19 and my ex was 1-2 years older than me. The DM (m) was in his thirties, and the rest of the party in between and all male, iirc.

I thought it was a cute idea to have a cameo and was super excited to join. It didn't go well though.

The party and my character met during a dinner. My Ex's character "flirted" with her, but it became obvious he wasn't very good at it. He meant to be sassy, but came off as offensive. And with everything he said he made it only worse. The party didn't seem to bother.

I reacted the way I would react if someone would speak to me like this in real life. My character became offended first. Eventually when he doubled down, I threw a glass of water in his face. I can't remember what happened afterwards, but the encounter came to an end shortly after.

The DM texted me afterwards being disappointed. He didn't seem to have any issues with the way my ex behaved - on the contrary, he said something like he had hoped that I would have acted out the romance, e.g. by giving my ex's character a foot job below the dinner table (he phrased it a bit differently).

My ex also didn't really understand why my character had acted that way and also was a bit disappointed. I think we never talked about it again and broke off not too long after. Looking back I can only think two things:

1.) How big of a red flag it was, that my ex thought being disrespectful was flirting. Didn't realize that at the time unfortunately, but luckily it didn't take me too long to break up afterwards.

2.) Did they really expect us to act out a soft porn in front of them all? Eww...