That sounds really scary for both her and your family. My grandfather started having similar paranoid thoughts at 83 and we didn't realize it could be a medical issue at first. Turns out it was a combination of things including a medication interaction and early dementia. Getting him to a specialist made all the difference because they knew what tests to run. You might want to look at
senior mental health doctor near me since they deal with these exact symptoms in elderly patients. The paranoia and confusion definitely need professional evaluation soon. Wishing you luck with getting her the help she needs.