My mum lives alone and is constantly messaging me saying my daughter (her grandaughter) is writing things on her bank statements when she isn't eg this is my money now? When I know for a fact my daughter works full time, has hardly any time to blow her nose, so it's not my daughter. She's even given her nan the house key back (to my mums). Please help. I'm lost what to do or think.
A daughter working full time and having little time would certainly not preclude her making withdrawals. I think that best thing you could do here is to go over the bank statements with your Mother. Try for the last several months.
If your Mom is unable to FIND her statements you should go to the bank with your Mother and ask for Statements for the last few months, make certain there is nothing unusual happening.
That would all be extremely simple and done in a day.
If your mother is showing other signs of dementia it may be time to keep a diary of incidents. Does she live alone? Does anyone have a POA? Is anyone helping her with checks and bills?
This is very little information for us to make heads or tails of, but it is very easily checked.