son and daughter in law are divorced son took his son and left due to unreasonable behaviour by his wife ,child would not stay with his mum and continually asked for a new one very hard to listen to he asked when he was 3 then again at xmas when he was 4 she had no real interest in him except when her friends were around. provided nothing for the first 5 years of childs life either .She had a better job and prospects ,he stayed at home with the child but was not allowed any money at all she would tell him to phone us the grandparents to sent money for nappies etc, we also paid half the bills as she insisted on that she was out most nights which led to him leaving and the child going with him ,anyway today another message to say it is sons turn to buy shoes he had bought school shoes and trainers from clarks for back to school plus uniforms she then asked him to send round some of what he had bought to her ,also if child goes to visit her on her days the lovely clothes he goes in dont come back always old stuff returned ,son has lost his job, she has a very high paying job but for the 20 plus years we have known that money is something she is strange about, she has suffered with mental health problems but seems ok at the moment she says she doesnt have any mental health issues no one would know that she was abuse in the relationship how do we handle this they have dual guardianship , just need advice really