If this can happen now...it can happen again...and again...it will be never-ending if the guy cannot control his feelings...if he can forgo what his gf has done for him for the last 5 years...over a girl he doesn't know well in say a few months...i seriously see no point in why the gf would still want to be with him...
He's a jerk just forget about him and move on...when he realise that he made the wrong decision and "beg" for your forgiveness...you'll realise he's even more useless then...
