Wow, been here myself op. In my dm's case it was a freelance hairdresser. My dm was a difficult lady and my concerns had to be broached very carefully and even then she became very angry with me. Before long, hairdresser's daughter was now the cleaner for my mum both taking money from her. It was clear there was little cleaning going on because I went in afterwards and had to do the same job. Before long, photos began appearing in the living room of the daughter as though she was replacing family.
DM's bank manager actually phoned me expressing concerns about the large amounts of cash she was taking out. I know this is strictly a breach of confidentiality but at least he cared. After he called, I went round to see mum and where she kept her money, well there was not a penny left out of a £400 withdrawal.
I did ring ss but they said there was no proof at all and as they were sending care workers in twice a day, then they would also be in the frame. They had been going for two years with no issues and the staff where the same.
When dm went into a care home, we didn't see them for dust of course.
I ended up falling out with my mum over these horrible people and I wish I had handled it differently but I felt completely powerless. I still feel guilt five years after her death.
I would arrange to go round when Anne is there and get a feel for her. It also lets her know that you have your eye on things. The red flag here is her telling your dm about her family issues and more importantly the administrative work she is doing which gives her an opening and insight into your mother's finances. Go with your gut instinct, it is rarely wrong.
It is sad to be suspicious of someone's kindness but there are sadly very few completely altruistic people.
I was a care manager and very sadly occasionally came across workers stealing from clients. The saddest thing I used to hear was that if they had known they were short of money, they would have happily given it to them. I suspect Anne may be short of money soon.