After MJ's kiss with Spider-Man and before being insulted by Norman and Harry MJ was shown to be a great deal happier and almost ecstatic, because it had perhaps been her first kiss with someone who loved her back for more than just aesthetic reasons and while she was kissing him, she most likely felt Spider-Man's love for her; something that would have enhanced the sensation of the kiss even more.
She had just had the most incredible kiss of her life, with a man suspended hanging upside down in the pouring rain.
He confronts MJ in her apartment and threatens to kill Peter if she does not break up with him.