I might be a little off, but IIRC, the "I love you game" is where the two players take turns "confessing" to each other, and the objective is to not to laugh or get flustered when giving or receiving the confession. Though it's not shown in the comic, presumably Ucchi already knew they were playing the game, but was so overwhelmed by hearing the actual words that it temporarily slipped her mind.
My point being, I guess, that I don't think anyone was being mean or deceitful.