Dad and a golddigger

I'm really worried about my dad and I don't know how to approach this. He's in his 80's and he's gotten obsessed with a woman in her 50's (younger than me) and she's taking him for thousands a month. He is also blowing off family events and celebrations to spend time with this woman - even missing a family funeral! Whenever anyone tries to talk to him about her, he gets furious, screaming and refusing to talk. She is taking him for huge amounts of money - hes' even given her a credit card that she uses with no restraint. Not only is he destroying his finances, but his destroying his relationships with everyone else because of her. I don't know how to get through to him.

With a lawyer If he wants to deny what is happening you won't stand much chance otherwise