But that's never even hinted at. I think we are meant to believe that they are just attracted to her.
Is that such a bad thing? She looks, sounds, smells, feels, and acts like a real woman. That's far beyond what a holodeck can normally provide. And, she's presumably "played" by a real person (I suspect Zero Zero). Combining her assumed appearance and the fact that she was effectively sentient for that reason, it would be odd if Riker wasn't attracted to her.