Everyone missed the part when the manage said the crystal surgery can affect her sanity, but its apparently too late since she prob turned into psycho yandere thanks to it
Im gonna guess they were engaged/married before she turned into magical girls, and as time goes by she works to pay for surgery so he doesnt die and get healthier, but at the same time her personality and mind altered so much he became afraid of her,
damn, bet he rather die than watching someone he love turned into something else entirely, someone can fight an eldritch octopus entity descend from the sky and dont mind being covered blood splatters