I don't care what is considered rude/awkward/disappointing by strangers which presumably a tinder date is. I mean what even is the harm to the guy here? Just ask what's going on and tell her why this has you on edge if it does?
And none of that is an excuse to be rude to someone, to hit on her friend to get back at her, that's just incredibly petty. And way more rude than just having with dinner or whatever with two people instead of one.
"yeah she did this thing that wasn't what I expected so now I'm gonna go out of my way to be rude to her" that's not a proportionate response. Are you unsure whether you misread signals? Just ask. Do they maybe wanna get you to pay for both, just ask?!
Why is the guys POV the focus here and not the girls who are being bullied??