I just went home to see my dad who lives far away and his new girlfriend doesn’t like how close we are… It concerns me because he’s getting dementia and she doesn’t want me to be involved in his life at all and there’s absolutely zero reason for this feeling. She completely denies that he has memory issues and I suspect may be there for the wrong reasons. It breaks my heart and is compounded by the fact that my father depends on her heavily due to his memory issues. So my question is what should I do? Has anyone been through a similar situation? I’m his only Child and I’m worried about him and I’m worried about her motives.
If he really has Alzheimer's you need to do some serious intervention or the girlfriend that is there everyday will be doing whatever she wants and you will have a tough time proving anything or getting your dad to talk against her.
Who has the POAs for your dad? If you do, use them to get him diagnosed so they can not be changed. If you don't, I recommend that you get them and get them ASAP.
Have you tried bringing your dad to your house for an extended visit to put some space in the relationship?
Bottom line is that he needs someone, so you step up or you will have to step away if he chooses her. You say he leans on her heavily, so immediate action is needed.
Good luck!