When Helen of Snowhaven disappears, adventurers from all over the realm are called to search for the missing princess. Kayle wouldn't usually care about it: she knew how hard it would be to find a kidnapped princess when the captors didn't ask for a ransom, but she got a glimpse of a cloaked woman that fit the princess's description while she waited at the gates of the capital to be granted entrance.
Maybe she was wrong, but over her large career as an adventure she had learned sometimes taking a few risks was worth it and paid off in the end.
And this wasn't any different. The woman she had seen was the princess, and she hadn't been taken by anyone. She had fled from her father when he tried to marry her off to a stranger, and now that Kayle found her, she asked for her help, asked the amazon to take her away.
Kayle was faced with the choice of helping the pleading woman, or delivering her to her father and get the reward he promised, a reward that would set her for life. In the end, the choice wasn't that hard.