My (30f) sister (25f) instigated a bar fight to show off to her friends and got concussion as a result. AITAH for not stepping in to save her?

She has a habit of approaching Random men and calling them "bitch" and "pussy" and getting in their faces. Her friends think it it's hilarious. I was out with their friend group and this time the guy took a swing at her and concussed her. Our parents found out and said I should have fought him for her because I am older.

I did get the bar bouncer for her, but I really didn't feel like I wanted to get into a bar fight she started.