It technically was not cheating, as in the bugged version, the MC still told Lily its ok to go ahead with Debbie, even if it ignored the player's choices and it made it jarring. But that's all it was, a bug, and this was a beta, so it's all but expected for some things to go wrong.
I'll have to commend the devs for generally being really accomodating for different options and paths, there's a lot to juggle to keep the story & characters coherent.
I know it was a bug, I was explaining what some of us saw in words others can understand.
Honestly, I hope the entire thing is redone, if you let the confession happen in your presence at all, you get a 3 some but Lily (even if you were 100% with her and loyal only to her), says she's together with Debbie and sleeps with Debbie. When you mouth "it's okay" you should have the option to say no, and if you admit that your relationship doesn't change between you two it only changes between them too, but your sleeping alone and not mentioned as the boyfriend anymore. It's not a very rewarding 3 some. I just think that entire scene needs a bunch of touch up is all. I get that it's complicated because you have essentially several routes involved with that scene and Ace said it's a work in progress and the other not pairings are a work in progress but this is a beta version, I don't think anyone is wrong here for anything they point out. Frankly I haven't even tested a Debbie solo path yet, I'm betting it's going to have alot of the same issues.
My concern is you have to be the asshole or get no content (currently) in order to do a Lily solo path. I feel it's not cool that Lily doesn't stand up for you at all. Don't get me wrong I'm glad you can stop it now but your options aren't that great. I think adding a "No" option to match a it's okay option would be beneficial so you don't have to ruin everyone's night but that's just my opinion and thoughts. I'm sure during full release everything will be figured out, hopefully we will know also by then for sure no matter which options you choose rather or not you still have a girl friend.