Seems Seliana came acros Mutu and wants to make the sharkess a bit more humble~
Reeeeaaaaching in, the sharkess starts to grow more fur, and lose some of that smooth black in favour of some blues
Having "borrowed" Mutu's soul, the former sharkess is just a blank slate, almost identical to the soul's new owner
And what's the fun of having an unused soul if you could use it to pad yourself out a bit. The other you doesn't seem to mind~