sounds like the best thing to do is consider moving that is if she starts coming and physcially destrying property other than that just ignore her
I think the paranoia can come from dementia. You might want to contact adult protective services just to make both of your lives easier. If she doesn't have a caretaker close by she sounds like she needs a guardian. It's possible she needs medical care that she's not getting. As they say, crazy people don't know they're crazy. APS will go and talk with her anonymously and call you to let you know what's going on. Otherwise, (you shouldn't have to move) just cut her off and ignore her.
neither bipolar or dementia , i have studied in these subjects for awhile now , if anything this sounds like classic textbook psychosis coupled with schizophrenia .. given her age i would do as above suggested maybe they could check if she is taking correct meds and/or whether she may need to be
assesed and/or admitted to hospital .. you would not only be doing yourselves a favour but also possibly stopping this lady from harming herself or in an extreme case others.