If you think this made the cheating better then you are wrong mate, considering that, she definitely knows how MC feels about Leon, how much he hates him, and that makes it worse and a bigger form of betrayal.
Like I said, "she gave in and made a huge mistake." I mentioned that she woke up feeling regretful only to note the guilt she's experiencing on the path in which Alan is faithful and supportive of her, as feeling guilt tends to motivate a person to try to make amends. Despite what happened, I still think there's hope for Clara and Alan to reconcile on one of the paths.
Before saying that, however, I was clear about how Clara was intoxicated, simultaneously manipulated by Anna and Leon, and then targeted by Leon's persistent sexual advances, despite her trying to pull away and telling him that it was wrong and/or that he should stop four times after he first forced a kiss on her lips. So there were mitigating circumstances that made her more vulnerable to eventually giving in and cheating on her husband. That doesn't mean it entirely excuses what she did (nor does she think it does), especially given Leon's history with Alan. I even mentioned elsewhere in the same post from which you quoted that Clara initially had thoughts about somehow wanting to get revenge on Leon for what he did to Alan when younger, so just imagine how much Clara would want to hurt Leon if she realizes that he played her for a fool in acting like he was so concerned about her and instead used her as a tool to further hurt her own husband.
And now, I believe I will cease from talking about this Clara and Leon situation for quite some time, as I have said more than enough about it. In fact, if you were to go back and look at my prior posts in this thread, I frankly have spoken about this particular issue ad nauseam, including having acknowledged several times that she could not have cheated with anyone worse than Leon in relation to the emotional impact it will have on her husband. Maybe she can try to start making it up to her husband at some point by helping to get revenge on Leon as she originally had in mind before she got played for a fool.