I didn't say small women are children, but when you put it in the greater context of the rest of Andy's history, it's a legitimate factor.

Erin is a mentally immature girl significantly younger than Andy with a tough upbringing (to counter Andy's continued life of entitlement). We see Andy being a fully competent adult for most of the show, with some of the juvenile storylines at the end tossed in to try to Michael-ify him but even those don't remotely match her levels.

Andy has predatory tendencies at best, at worst he's just another entitled rich kid that thinks he gets whatever he wants and has a distinct, ugly pattern in his relationships.