Can my sister change beneficiaries on a insurance policy to benefit her when we have have both been left 50%? My dad has dementia.

I can't see an insurance company allowing anyone other than the owner making changes to beneficiaries. I can see your half sister influencing him to call and make the change. Unless you can prove he is incompetent, not much you can do about it.

Just read, that to change beneficiaries concerning an insurance policy, it has to be written in the POA. POAs cannot change Wills.

Without a POA your sister cannot do much. I wonder how she sold the house without a POA. If her name is on his accts, not much can be done there. But the sale of his house? She better know what she is doing. It should have been sold at Market value if Medicaid is ever needed. The proceeds going to an acct for him. Anything spent out of that account needs to be for him only. She needs to keep very good records. Just being his daughter doesn't give her rights.

Here is what you wrote in another post: "My name is Marie and I live in the texas ,my dad and my mum had a fling while he was stationed in the UK 57 years ago. I met up with him when I was 30. He has one other daughter Kasey who lives in Hawaii. My dad has been living with my cousin for last two years while he battled cancer then again this year. He has dementia diagnosed in 2019 and needs a lot of care. My half sister has collected take him back to hawaii to care for him as she doesn't want to use money from the sale of his house to use for his care. She is going to set him up in a rental my dad thinks he can still drive it his license has been suspended and he won't have it. My sister is on my dad's account so she can spend his money as she seem fit. What are my options."

Where did your father live for the past two years? Where is your cousin? And where did he live before that?

If your sister doesn't want to use the money from his house sale for his care, then what is she doing with the money?

Have you seen the will where you and your sister have each been left 50% of the proceeds from the insurance policy?

No POA? Only dad can make changes. Maybe she used undue influence? Dad NEEDS an attorney and possibly a guardian and conservator.

I agree with all. I myself think that no one can do this, and they CERTAINLY cannot legally do it to enrich themselves. I would NEVER attempt to do such a thing without seeing an attorney lest I got charged with fraud. Esp. if this person is a POA which makes them a legal fiduciary who could be sued and jailed for fraud. See an attorney.

She'd be guilty of fraud if she did, and especially if she holds power of attorney.

You could remind her that fraud is a serious crime, as is exploiting a vulnerable senior. You could sweetly offer to check with the local district attorney's office to get all the details for her, too. ;-)

"The policyholder is usually the only person allowed to make changes to your life insurance beneficiaries. 

If you’ve granted someone a power of attorney—a legal document that lets someone make financial, legal, or medical decisions on your behalf—they may have the right to change your beneficiaries. No one can change beneficiary designations after the insured dies.

There are two circumstances when you need another person’s permission to update a beneficiary: if the policyholder lives in a community property state or if they designated an irrevocable beneficiary."

Source:
https://www.policygenius.com/life-insurance/can-you-change-your-life-insurance-beneficiary/?utm_source=google&utm_campaign=c:sem|p:google|v:life|b:nb|d:dt|a:all|i:all|m:dsa&utm_medium=cpc&utm_content=527288553794&utm_term=&utm_location=9012429&utm_device=c&campaign_id=12560016618&lptest=&gclid=CjwKCAjww-CGBhALEiwAQzWxOgdiSh7ZLpj9oEUYTocRIq4kUxnEAyUVSr4AG7OmzE4Ux5JXjW6zzBoC_1EQAvD_BwE