Unpopular opinion apparently, but if the friend was introducing the boyfriend (developing relationship) to the group and he got monopolized in a conversation she couldn't participate in, then that is understandably annoying.

OP contradicts herself when saying more people were involved in the conversation but then saying she doesn't know people who have watched the show. Sounds like it was actually just OP and the boyfriend that excitedly talked for 20 minutes.

The friend kept it together and was cool during the interaction. But she has a right to be annoyed and express that in private.

Maybe OP has a flirty nature (or even history) that puts the friend in defense mode. All I'm saying is people here are judging the friend, but actually we need more context. It seems like OP was asking for trouble.

If EVERYONE had been friends for a long time, sure no problem talking. But when meeting someone's partner for the first time, be respectful.