Etymologically, “bestiality” would seem to be best defined as “sex with a beast,” i.e. a nonrational animal. So I think Lois is O.K. to the extent that Supes counts as rational.

On the other hand, I’m not sure that he counts as an animal at all — at least, as the term is used in contemporary English. Your argument seems to presuppose that it’s the name of a functional or structural kind, rather than the name of a particular biological kingdom. If it’s the latter, then the natural kind can’t include anything that’s not interrelated with the other members of the kingdom, meaning that, except on a theory of panspermia, no alien life form at all could count as an “animal” except in a scare-quoted, analogical usage.