Hi
This is a bit tricky. Parkinsons and dementia do tend to go hand in hand. Delusions and hallucinations are part and parcel of dementia and it's a horrible, distressing thing to witness.
My mum went through some pretty awful ones. The most common delusions/hallucinations are: people stealing from them, partners cheating on them, people trying to poison and/or harm them. That's not to say that these things don't happen but they are very common because the brain with dementia can no longer make sense of the world around them and they don't understand why so the brain is trying to make a 'narrative' for example they can't handle money any more so people are stealing.
Sadly, these feel completely true for the person with dementia - they genuinely believe what they are saying, no matter how outlandish it seems. If these are delussions etc - these are called 'false beliefs' and will probably continue and sometimes get worse.
The first thing I'd suggest if trying to figure out *what* you're dealing with.
Firstly talk to your mum's GP, explain what's happened and request (insist if you have to) that your mum is tested for any urinary infections. These are very common with dementia and can cause delusions and hallucinations, and infections need to be treated asap. If it's caused by this, the treat these should stop.
If there's no infection this could point towards delussions etc.
Secondly, I'd strongly advise you to consider putting a small camera in your mum's room - ideally somewhere unobtrusive where people won't see it. If your mum is being abused, you might be able to capture evidence. You can easily buy these on Amazon, if you have an Alexa, you can link the feed to your phone and check her room remotely. This will also help you rule in/out what's actually going on.
Also examine your mum - does she have any bruises, marks, rashes etc - does anything look out of the ordinary for her?
Consider talking to the manager at her home. I know this is potentially tricky if you're worried about abuse, but not communicating is one of the worst things you can do. Express your concerns about your mum and pay close attension to how the manager reacts, not just what they say verbally but do they listen to you, take you seriously etc.
With dementia, you really need a brain scan (CAT or MRI) to diagnose dementia. You could ask your GP for a referal but waiting lists aren't good. If you can afford to, you can get your mum a CAT/MRI done privately but I understand this isn't always possible. If you're able to get the scan and she has dementia, then you ask your GP to refer you to the memory clinic.
Generally, the advice with delusions/hallusinations is just publically agree - basically, even if what they are saying is crazy, agree to their face, and don't argue/reason with them, it won't work. This is easier said than done. My mum had some pretty bad and nasty delussions and hallusinations but some were just weird - for example she'd keep pointing out the 'new' car my stepdad had bought that was parked in our back garden.
With the police, you could try a few things. Tell your mum, that you will ring the police for her - this may soothe her that she thinks someone is listening - but just be warned that people with dementia become fixated, no matter what you do, they'll keep mentioning it over and over and they may become hostile to you if they feel you aren't on their side. It's a horrible, tricky situation. Just don't try to reason with her. Instead try things like 'that must be horrible mum, I'm going to contact someone to help you'
If you have genuine worries about abuse, contact adult social services, and get them to talk to your mum - or even if it's delusions I'd still advise getting social services involved, they can give help and advice. Or contact the police yourself. The police had to get involved with my mum when her delusions got really bad and she became dangerous. They were amazing with her. I think a lot of police have to deal with this stuff a lot.
Do you have other family that helps? It might be good to sit down together and all agree what to do together. Maybe arrange unannounced visits at the home and have a rota - have people check for injuries just by looking her over.
Also talk to the carers themselves - you don't need to say what your mum said, but ask how is your mum doing, what is she up to etc. Again notice how they act/respond etc, that should tell you a lot about how they view your mum and their attitude.
You can get really good advice from the Alzheimer's society - you can email or phone them. Another organisation Admiral Nurses also offer excellent advice about dementia and how to deal with things. There's Age UK that can help as well.
Please keep us updated with how things go