User blog comment:Wrath022/Chapter 524: Black Future, Review/@comment-6401212-20170225223416/@comment-7418318-20170227215408

Maybe he finds her so cute that he'll want to take her as his pet or mascott. ^^

Or on a more practical note, maybe he'll intend to force her to serve him for the time being as his personal medipack until he finished off anyone else who might be able to hurt him, maybe even with the option to be allowed to live, if she faithfully serves him.

Not sure if I'd like that, but at least it would make logical sense from certain angles... not that Acnologia has much to do with logical and rational decisions.