His mother mourned after their wedding what called off. Mourn is a verb with means "to feel great sorrow."

"Lamented" would be a good word here. It is used in modern English. Her mother lamented that the wedding was called off. All those years of planning wasted! "Bewailed" can be used, but while it is used today, it is very uncommon. I think "mourned" is actually good here. I think the mother felt as if something had died. "Very sorry" isn't strong enough, nor is "regretted".

Her mother felt bad after their wedding was called off. All these years of planning wasted !