Brunette woman will win.
She will dominate blonde quickly in front of man.
Fight will started for several knocks both women. Brunette first will hit several goods blows in face. Blond woman will defend hitting with smacks. Brunette will catch blondwoman's hair and inclines her. Brunette will hit fists her rival after backings. Brunette will overturn on the ground blond woman, pull at hair then. Brunette will sit down on rival's backings or belly and gives her great beating.
After this blonde will have to go away. Brunette and her man will be lovers.
Different possibility exists yet.
For example:
Before overturn blond woman will catch brunette's nipple and pinches him. She will catch for hair brunette then and kick her knee in face. Pain will fuddle brunette. At this juncture blond woman will beat rivai in ground very bad and win. There now I think from this is less probable.