Her height has nothing to do with anything, but people like those sorts of details. Maybe we instinctively feel that a 4' 11' woman with the last name of Gomez gets under-estimated constantly, so it makes her success more satisfying to us.
Her height has to do with people's assumption that bounty hunting is primarily a physical, violent activity: going and wrestling a dude into submission and then slapping handcuffs on him and dragging him to the police station.
The reason they mention that a very small woman is very successful at it is to point out that success is not predicated in being able to win fights with fugitives.
I assume that is what hired muscle is for. She's the brains of the outfit. Did anyone else think 10 grand was kind of low for this particular job? They did mention she would get the reward money, but didn't say how much that was.
