Kei's not a Jedi. If she dies, she doesn't become one with the Force - so Kamor Bakhva is useless in bringing her back.

Besides, as we know from Requiem...

	"But we -haven't- seen her, and Teleute and Forseti haven't
either," Vigdis confirmed, "so... there -is- hope.  But I don't want
to give you too much of it.  She had... has... very powerful enemies.
Everyone who was at the Ragnarok has."
	"Powerful enough to interfere with the natural order of
death?" Kozue asked.
	"Yes," Corwin and Vigdis replied as one.
	"... wow," said Kozue softly.