Speculation in the comments is that Halea is wearing out and her puppeteer is looking for a new body. Some have noted a slight discoloration of her skin peeking out from behind the ever-present green scarf. I'm not convinced that means she's dead, if only because sending Halea to Cheth would definitely give away the game. But her body could still be having a bad reaction to its overbearing extra occupant, a problem a prettied-up zombie wouldn't have.
It probably also means something that, despite the decayed condition of her body, Phaedra is not actually dead. Not entirely. She won her life back, after all; her ghostly state is because that life is being shared among her friends and dog. I wonder if that is part of why "Halea" has plans for Phae's body: It's (arguably) not technically a dead body, but it is unoccupied.
Have to feel for Daphne, at any rate. She thinks she's surrounded by friends and fellow mourners when instead it's two puppets of a hateful, scheming goddess.
As for who that goddess is? The obvious answer is Cheline but her villainous demeanor here doesn't quite mesh with Cheth's feelings about his sister. Is he simply wrong, or is this creature no more Cheline than she is Halea?
(Also, speaking of mysteries, we still don't know who Snowbelle is. My guess is Euphemia but I'm not laying down money.)