[quote=NarcissisticPotato]
What I'm trying to work out is why exactly Kast would take her with him? If he knew her properly then he wouldn't dream of taking her! Maybe she does best him in combat? Or maybe she's particularly persuasive?
[/quote]

He probably doesn't know her properly, and it's likely he wouldn't be 'persuaded' by her. He's about as emotional as a rock most of the time. Since he's super professional, he's probably recognized her as an viable asset during various bounty hunts, where her feminine charms and surprising combat skills would allow her to more easily get into places where a heavily armed and amored Mando couldn't.

She could easily work as a con artist, which is always useful in Kast's line of work.