You made a reservation and accepted the strict cancellation policy. No mistake there. Then, your ex changed his mind. Again, no mistake. None of this falls in the extenuating circumstances policies that might give you the right to a full refund. That way, only if the host is willing to give you the money back, you will have a chance to get it. So,for all i see, you and your ex are the only ones to blame, not the host, who just enforced her cancellation policy, as it is clearly depicted in the listing. Be more carefull and aware of things when making a reservation and remember: to you,it´s vacation, to them it´s a business.
Regards