The two were associated before he bound himself to Merdia's realm. They were said to be lovers, and she lent him an army long before immortality.
Could it be that consorting with Umaril was the reason that Magnus booted her in the first place? To put it another way, could Umaril the Unfeathered be the "ilicit spectra" that was her downfall? If so, and now that Umaril is gone, could we see a change in the nature of Lady Meridia?
How many divine entities were changed during (and slightly before) TES IV?
Dagon got banished.
It appeared as though Akatosh may have either been grievously wounded or killed altogether.
"Sheogorath" is now a former mortal.
Jyggalag is set free.
Azura was...ummm....violated and exploded.
Talos' place in the Divine pantheon now challenged by Pelinal's mythic return.
Meridia's potential "bad influence" being destroyed, which may allow her to return to Aetherius.
Lots of changes, my friends.
___TWM