Right?!? It's not a gift at all! If you made plans to lease an apartment and the landlord gave you the keys, and you then changed your mind and decided not to ease the apartment after all, would you then keep the keys?!?
Of course not....an engagement ring isn't simply "a gift"... If he just gave her a ring for her birthday of course she would be entitled to keep it... I have plenty of jewelry from ex boyfriends, some of it quite spendy, but it was birthday gift, Christmas gift, I really really like you gift.... Not an engagement ring.... A gift is given out of love, an engagement ring is given with the expectation if marriage... You get to keep the engagement ring as long as you are engaged...(or married)... No engagement, no wedding, no ring!!!