Yeah, I too miss some butt expansion in this. ;3 There was a moment I had started creating the sprite for it for the slime girl during development, but it was tricky because of the cauldron that is narrow and I had to finish fast.
At first the spell's star would split in two by hitting the cauldron edge, one slides on the slime girl back and goes to Emily, the other goes high and land in the slime girl's butt before sinking and getting absorbed. Both then would grow.