Grandad with dementia

Hi I hope it’s okay I post this here, but has anyone cared for an elderly loved one with dementia that has turned on you because of someone they think loves them. My grandad has dementia and has a women in his life who takes his money, and promises him fake things. Recently she has told him something or done something that me and my mum are the worst people in the world. He has been extremely aggressive towards us. But the women who he think does everything couldn’t hurt a fly. I’m very dissapointed because this is not who my grandad is. And I’m well aware that things change when they get dementia. Today out of aggression he told me he was getting “L” to take out a loan on his house for $50,000 so the health care people couldn’t put him in a home. But asked her to do that because my mum and I are unreliable which is not the case. There is a social worker involved in his care and she doesn’t think what “L” is doing is wrong. What do u do. Or why did he flip. I’m extremely lost. Any advice would be great. He rings me 12 times a day it’s very rare for me to miss a call.