I'll say it, she's a pedophile
Strictly speaking, that'd be more applicable if she was attracted to him
because he's younger. His age might also put him under the other term if that were the case too. Hebephilia, Google-sensei says that's for 11-14 or so? Don't get me wrong, if she crosses the line she's totally still a criminal. I just prefer precision in the use of terms. Actually, if we want to get super duper technical, depending on the part of Japan, they might be able to handwave a relationship as long as his parents give it the okay. That may or may not still be a thing? Not entirely sure the child protection act got rid of that part of things. I would hope it did, to be honest. Not much of a protection if some parent could essentially whore their kid out to some rich dude or lady am I right?