The sad thing is that even catching MC and her mom red-handed may not be enough to break the spell. The spell is having a really odd effect on her state of mind. It is kind of like that scene where she cannot differentiate between her mother and boyfriend fucking or the two teenagers who she really caught. There are also several times where they are fucking perilously close to her and she is completely oblivious like the cuck in an NTR story. In the bathroom and behind the couch are two especially egregious examples. This moronic obliviousness and ability to swallow bullshit explanations with a smile despite the fact that she is so suspicious that she is hallucinating their liaisons when nobody is around could be a result of the spell. As a result of this, she may not be able to refute any explanation that they do give why she isn't seeing what her lying eyes are telling her.
One thing is that the spell makes her submissive and gullible about their affair, and another is that it doesn't affect her if she catches them red-handed. After all, look what her first reaction was when she thought she caught them in the dance party at the high school: she was outraged and furious.
It's true that the spell will probably get stronger as time goes on (we can see it in any of the NTR routes, where Chloe points out that she hates the library because that's where she met MC and they started their relationship), but I don't think it's powerful enough for her to accept their affair or whatever lam excuse MC and Nicole might give her if she catches them red-handed. Also, surely the first thing Chloe would do after discovering their affair would be to tell Beeman and/or her father, generating a real mess of hardly predictable results.
As for the situations you mention where she was able to catch them (the sofa and the fuck on the washing machine), she was distracted enough not to delve into the situation (on the sofa, she wanted to talk on the phone to her lover (MC en Non NTR route; Beeman in the other routes) and in the other, if I'm not mistaken, she was studying but with the headphones on). It's true that these are scenes typical of NTR moments, but within the possibilities, it is not as forced as it happens in other games.
Changing the topic, it's very likely that Orb will announce something in about three weeks. Before you ask, I don't have any proof of this, but based on his previous Patreon announcements, during the last year he's making announcements around the first week of every 3 months, and the last announcement was the first week of May. Following that pattern, he should publish something during the first week of August.