This is the fight I would love to see the most. It would be between my GF who is the brunette, and her Ex's sister (blonde). She told me they never liked each other before, but when she broke up with her ex, his sister started rumours about my her which were lies and since then they've openly hated each other. Some time has passed and it has cooled down a bit now but if they were both in the right place at the right time it could ignite again.
I would say it's an even matchup, I think they would be in the same weight class but the blonde girl is a little bit taller. I know both have experience getting in fights as well so it would be a good one.