When she died, her mother resurrected her. And just like herself in her previous life, she loves her mother dearly and obeys her every wish and command.
She's amused by how much Zoey doesn't trust her anymore. That's fine, Denay never really liked how close she was with Lullaby, anyways.
Zoey knew from the millisecond Denay came back from the dead she didnt trust her at all. What was once a choatic energy with joy and excitement had become nothing but Malice and dark intentions. But Lullaby never seemed to notice it... So despite her better judgement she kept her mouth shut as not to break Lullaby's heart. After all, it was possible it was just Zoey's immediate distrust in things that made her feel so uneasy around Denay.
While her previous younger self might have thought of him as a good friend despite his sour attitude, this Denay registers that he isn't her 'friend', but she doesn't mind him being around since he's with Rezon. Otherwise, if he was near and spoke ill about her or someone else she cares about, she'd not hesitate to rip his head off.