It was actually quite sad that Rodolphus convinced himself that she would make a good enough substitute for the witch he really wanted. That wasn't any sort of life. And what if Hermione decided to give in to the fantasy? He might be able to believe he was happy for a short period of time, but then he would grow to resent her and likely even hate her. It was nothing more than an illusion. They would both end up miserable. She was thankful that she'd had her wits about her enough over the years to keep from developing any misplaced feelings.