How do i go about complain about a nurse making false claims about my late mums cause of death?

my mums past away in may she had lewy body dementia but her cause of death was bronchial pneumonia but after several weeks after losing mum one of the district nurses told a none family member that my mum had died of cancer this came has a big shock to us becouse at no time had this been said so i wrote to mums gp to find out what was going on he wrote back saying my did not have cancer so i want this nurse to know how much hurt she a courses by gossiping hope you can help