My idea is that Leora is chatting with different peoples. If you notice, Leora can chat for hours and hours, too much time to chat with just one person. The other person will have a work to do, need to eat, or go to the bathroom or just sleep.
It's funny because Paul doesn't have all this control. Leora was even able to masturbate next to Paul while he was sleeping... I mean, if Leora wants to masturbate, she'll do it regardless of whether Paul is in home or not.
I don't know if I translated correctly but what you're saying is a contradiction. If Leora wanted to fuck Denis she had plenty of opportunities, and yet... nothing happened, nada, zero.
It doesn't make much sense; it's more likely that Paul will become more suspicious if Leora doesn't wash at home. As has already been said Paul may be an asshole but he's not stupid. They've known each other for more than 10 years and Paul knows how many times Leora can wash herself in a day.
She always do, so it's not a surprise. She has done this several times in the past, even in Russia. Sometimes she exit without underwear, sometimes without a bra, sometimes both.