Well, forgive her for not having the energy for being mean to him. Although honestly, the more time passes, the more she disassociates Andrew with the actions of the Doctor, and the more she disassociates the Doctor with her being locked up. She doesn't want to carry that anger and bitterness forever.

"I suppose even the most benign seeming transformation can be horrifying to some people," she answers. "Whereas some might actually enjoy the horrifying ones." Would the Master have minded being an undead minotaur? Who even knows.