Kaya was a member of the search party that was searching for Cheryl.
She scouted a park for signs of Cheryl, and could not find her. After the BOS Scout was killed, she refused to go any further and headed back to Canterbury Commons, leaving Manny on his own.
Since there is no Kaya either in Canterbury Commons or anywhere else in the game, it is plausible to assume that she died while she made her way back to Canterbury.
Kaya is only mentioned in Fallout 3.