Even if it wasn't her intention, it still happened. The guy literally worships her panties.
You can have an enormous impact on someone without meaning to, especially when they're extremely young and still developing. And that creates the kind of power imbalance you were talking about. Not physical, but emotional. Even much later in life they could still have an attachment to you that isn't completely rational.
That's why, if you've known someone as a child you should probably just...not. In general. Like, go find someone else. There's a whole world full of people out there. You don't gotta fuck family members, friends' partners, people you knew as kids, etc.
Again though, this doesn't doesn't actually apply to Rudy. Because he's actually in his 40s. But, again, they don't know that.