I think that the fact the mother has crown rot is another reason to leave it on.
The Keiki will draw energy from the mother and maybe that will weaken the mother. But it will minimise stress on the keiki which may not be big enough to support the blooms on it's own.
So maybe leaving it on will be a case of sacrificing strength of the mother for the sake of the keiki, but if the mother is going to die any way that does not really matter.