It has been previously revealed: Xing Lan is a hybrid.
She is a child between 2 women: a vampire and a werewolf. (c57)
She is normally in werewolf form, but the vampire blood makes her unusual in some ways:
- She is unable to fully transform into a human and has to rely on an illusion to hide her ears from humans. (C3-9)
- Sometimes the full moon brings out a vampire transformation. (c28-32)
Since her wings seem to have come out at will this time, maybe she is finally going to learn to control her body properly.