He dated another girl on a romantic holiday they went together
Some guys seem to have no idea about a proper breakup etiquette. This guy took his girlfriend on a romantic Pacific island cruise for her birthday. But he invited also all his mates along. And, to make matters even worse, refused to have any time away from the boys. She left him to it and went to do her own thing.
One night she saw him on a romantic date with another girl, taking selfies and drinking cocktails as the sun set. She had to spend a week stuck with them. As soon they got home she kicked him out.