Alzheimer's or severe PTSD

welcome to the forum. Your instincts are probably right, it's probably Alzheimer's: but there are a number of treatable medical conditions that need to be ruled out. One strategy a lot of folks here have used is to tell her an annual visit to a doctor is required or she will lose her insurance. Then, you should give the doctor a detailed description of your concerns and her behaviors before the visit--probably in writing. Medications can definitely help, these are not things (especially the paranoia) that can be handled without meds, typically.

You need to also be sure you have medical and financial power of attorney for her. this can be done through a certified elder law attorney (look at nelf.org).

Get her in to see the doctor because she needs to be seen or she will lose her insurance, typically Medicare. You can tell her you think it's BS, but you already had to do it to keep yours intact. Make her think you agree with her, but there's nothing that you can do about it.

"but there are a number of treatable medical conditions that need to be ruled out." It needs to be treated ASAP if there is a reversible problem. If you wait too long, the treatment may do no good. It may not be a treatable condition, but the stakes are too high not to pursue it.