Winged Horrors are the only thing I can think of, albeit it seems odd given she's normally moping off to the side away from the action. But I've seen them target some pretty random characters... And when they pick someone, they fly directly to them... Of course, there's also the potential that the "In fear" AI made her run away, into the curse.
The battle at the grove is also a possibility (I'm not sure where she is during the battle, but I wouldn't be too surprised if some enemy could bum-rush the main part of the grove for some wacky AI reason...)
Also, you can never rule out the game borking and just killing a random NPC for no reason. I know I've had Roland die randomly after I talked to him on several occasions...
