The only thing I can suggest is to Google her name/phone number with him there. There will most likely be other hits, showing that she's run this scam with other people.

Problem is, even that's normally not enough to convince someone in the middle of a romance scam. He'll call her, confronting her with the evidence, and she'll deny everything, convince him all over again, and then use a new name and phone number for future scams, knowing that this one's cover is busted.

As an operations manager at a large bank, I've been in the situation where I had to try to convince someone that they were victim of a romance scam. It came to my attention when she was re-mortgaging her house in order to send him even more money. She had already sent him $75,000, and was planning to send another $150,000. For months, I tried to convince her that this was a scam, and there were a few times that I thought I had, but every time, she called him again, they talked for eight hours straight, and she was convinced all over again. Never have I been more saddened and frustrated than dealing with that whole situation.

Eventually it got to the point where we had to cancel all of her credit with us and call in her loans, because it was obvious that she was going to send him the money no matter what, and we wanted no part of it. And I still lose sleep at night, frustrated at myself that I couldn't convince her not to fall for it.

I'm sorry I don't have a happier ending, but there's regrettably nothing that will reliably work in this situation. As long as your father is still of sound mind, he has the right to do with his money what he wants, even though he will lose everything.

I'm so sorry you, and he, are going through this.