He saved her from certain death on Tatooine. Originally, Boba asked her to help him reclaim his ship and find his armor as payback. She was free to go after that. However, she decided to stay with Boba Fett and join him in other things that he was planning to do. She was a wanted assassin with a large bounty on her head at this point. So, staying with Boba was wise as they could look out for each other. At this point, Boba Fett also went through a lot of character growth, and he valued loyalty over money for bounties. The two of them were no longer bounty hunters. Instead, they were starting to build a safe and secure empire on Tatooine.