so she couldn't have sex with him just to satisfy herself?

was attraction a requirement for sex to happen in this situation?

maybe, just maybe, she was horny for sex, she's had sex with him the past, she may have remembered that it was good sex and that since he was available, why not take advantage of that fact and have sex? PH wants his wife back, she knows this, she keeps him at a distance, for what it's worth, she's in control here, that mindset satisfies her ego quite a bit, she likes being in control, maybe she had sex with PH to screw with his mind as well as his body, so many what if's....

again my point in all of this was reading too much into it and making yourself ask a ton of questions that you will never really know the answers to unless she's here and speaks truthfully about what happened.