if she refuses to see anyone at all and she's a danger she's probably going to have to be taken to hospital to be assessed and they can legally do this as you are clearly both at risk
Try mental health services for older people Llandough 02921 862 6700
If you are not in Cardiff and the Vale let me know and I will get the number for your area . You are doing the right thing asking for help but you must act NOW .
Everyone is with you mate , I have been there with my father and mother who exhibits the same behaviour as your dear wife
Take care bluebird