What if Liam isn't cheating, but Sophia thinks he's cheating? Maybe she catches him in a situation that makes her believe he's cheating on her, and instead of confrontation, she feels relief, that now her finally cheating on him is allowed. Maybe the scene at the clothes store in the beginning of the game was a setup for that kind of story...While I think this idea is hot, the fact that L&P has said that Liam is not cheating pretty much makes this idea a fantasy. Until/unless we get some actual evidence that Liam is cheating, I'm going to assume that L&P was telling the truth.