I used to know the source for this, but I don't remember what the manga's called. Earlier before this the predator, which is some sort of demon version of the prey's mother being controlled by the bade dude. Hugs the prey while in a more humanoid form and absorbs her into her body as if it were made of liquid.
the prey manages to escape, one thing leads to another and the pred becomes the big bird monster. eats the prey as we see here but absorbing her daughter freed her from the antagonist's control.