She doesn't really enslave him... it's more blackmail! And her alternative is for both of them to be captured and enslaved anyway!
The whole story is based off an old Chinese story called Journey to the West. It's there that the theme comes from, back in the 1500's. It was toned down massively, and greatly simplified... The original monkey was:
The first is Sun Wukong, or Monkey, whose given name loosely means "awakened to emptiness" (see the character's main page for a more complete description), trapped by the Buddha for defying Heaven. He appears right away in chapter 13. The most intelligent and violent of the disciples, he is constantly reproved for his violence by Xuanzang. Ultimately, he can only be controlled by a magic gold ring that Guanyin has placed around his head, which causes him unbearable headaches when Xuanzang chants the Ring Tightening Mantra.
I am getting a feeling that you have a personal issue with the theme, and are disliking of it, whatever the way it is meant. I have themes like that too... Like I hate stories where bad guys are 'Evil; just because' as I am a great believer that people are inherently good, and only do things that are perceived bad because of other justifications, or because that is what they honestly believe is right... But that is a different discussion or issue!
I seriously recommend that you play the game, and see the characters! The acting is spot on, and the gameplay is actually pretty good too! If you still think the same after, then it would make for a much more justified discussion!