It’s rare, but it happens. They’re consenting adults.
E: look, I’m not a fan of this age gap, but everyone’s making up rules about what’s acceptable. Either they’re adults or not, 18 is the cutoff, and if no grooming was involved you can dislike it all you want but they’re still adults.
E2: looks like they met when she was under age. So, no…this doesn’t work right at all.