What has anybody done to help them with dementia other than trying to talk to the doctor about it?

I’m not really sure if my grandma has Alzheimer’s or if it’s dementia it hasn’t been talked to by a doctor but over the past three years it has progressed to the point now where she believes that the neighbor actually comes inside of our house which is absolutely not true. I have cameras pointing at every single exit and entrance of our house. She claims that he stole her file of important papers and her whole purse with everything she has in it and she claims that she heard some little girl get raped and that the next-door neighbor knew about it and didn’t do anything so she went down to the Police station and file a report and claims that whoever raped a little girl ended up getting arrested and that she hears the mother cry all night long. She claims that she hears the neighbors fighting. She claims that she can hear me and my boyfriend talking. She also says that she can see three men outside one with a mustache and she can see the reflection of them on their wall and that they have this little camera that flies around in her bedroom taking pictures of the inside of her house. I’m just really young and unsure what to do because she gets mad at me whenever I try and explain to her that these things aren't happening. I did in the beginning agree with her but that seemed to only make it worse because it would just lead onto something later that I would have to agree with would be completely false so now I just try to explain to her that everything you tell me I can only believe the facts and the facts are the cameras & police versus what you keep telling me you are “hearing.”