Welcome, Changeling!
What an interesting challenge. I could see Lex thinking that whatever he wanted SHOULD be his, whether said woman was married would be of little consequence to him. I could see him finding it a game to see if he could wedge them apart to get what he wanted.
I read a comic once where Lex Luthor came into restaurant and flirted the waitress, coming on to her. She rejects his offer a night of bliss, because she is happily married. He, then, offers her an indecent proposal: A large sum of money to sleep with him. She keeps refusing him, and he keeps upping the money. She and her husband are very in debt, or he's sick, or they have a sick child (I can't remember which), in other words, the money would be very welcome. Finally, she relents. Lex tells her he'll be waiting for her in his limo. She clocks out and with heavy heart with her decision, she exits the restaurant only to watch him drive away. He was only toying with her. He wanted her for free and the offer of money was only a ruse to repay her for rejecting him.