I just wanted to preface this that I am not a brocon but as the youngest of the three siblings with two older brother who are already married, you would definitely hope your sister-in-laws that vibes with you. Thankfully, my current sister-in-laws are all nice people that I can go along with. I know the hating bro's gf in this story is annoying but honestly from my own personal opinion you wouldn't want someone you couldn't get along with as your in-laws.
Thank you for coming to my broco- TED talks