Father 85 lives with lady friend, who has had and has multiple health issues, mental and physical. I get no return phone calls, leave messages text her she says she won’t have texting conversations. I asked for updates and get vague answers. It's all about “her” and her ailments. Spoke today, started bashing me and blaming me telling me my father cannot follow simple commands, dress, shower etc. She didn’t let me speak to him. I call and she monopolizes conversation about her health and gets nasty verbally.
My dad had a wife that wasn't overly particular about his health and wellbeing, so I would call the local sheriff and ask for a wellness check.
This actually worked really well, because she knew that I was not just going to look the other way and let her do whatever she wanted and it put them on the radar with law enforcement, so if anything happened there was already a record of issues. She got out of the way of me checking on him.
So I highly recommend involving law enforcement and tell them that you can not get through to your dad and you are very worried that he is not being cared for.
One thing, he picked her and she is doing the hands on, boots on the ground caregiving, which is brutal, especially if she is not well herself. So remember to appreciate what she is doing for him, it is a big job.
My dads wife didn't even cook for him. She was always out spending the money and she didn't care if he had food as long as she had everything she wanted. I would have felt very differently about her if she was actually takin care of her husband.
If its found that Dad needs more help than she can give, then do whatever you can to get him help. But, I wouldn't take responsibility for her. And I would make that clear. The state can take over her care if she is found incompetent too.
I do think OP needs to get access to any significant financial assets, and look out for abuse.