Asking for compensating ex-fiancee for physical and psychological harm

Hi

I got a legal notice from my ex-fiancee demanding that I pay her X amount of money for canceling the wedding about 3 weeks prior to the event.

She claims that I caused her physical (we had both equally paid some advance amount towards wedding venues) and psychological harm by canceling the wedding. I called it off after warning her several times to correct her explosive and abusive temper and blatant lies.

What is my best course of action here?

Thanks!