I think if someone implied they were bringing someone without at least asking, as this person did, I would match their rude energy and say “I did not agree to that, so here are my boundaries.”

The way the other party phrased it would annoy the shit out of me. 'I’m bringing my best friend." Ok, so why don’t you date them? Causes way more friction than asking “Hey, I know it’s unconventional but I would like a friend to be there just for my safety since we don’t know eachother yet.”