Another thought: This kind of behavior could also be associated with depression, with or without dementia. Another reason to see a doctor. Depression is treatable.
I'm not quite sure what you are asking. Is this how WHAT starts? Dementia? You said she's experiencing dementia, so I would say that it has already started. I will tell you that everyone's experience is unique. Have you asked her why she is nervous? What does she tell you? I think that if the day comes when I begin experiencing severe memory loss, I will also cry.
Have you taken her to the doctor about this? What does the doctor say? Has she had any memory testing? She might do better with an anti-anxiety medicine. It might calm her down some. I think I would start there. Best wishes...
If it is a medical diagnosis I suggest talking to the doctor who made the diagnosis and asking about possible treatment for her crying and nerves.
If it has not been medically confirmed, then I think the starting point is to see her doctor and have a complete evaluation done.
Either way, this is a behavior to discuss with medical professionals who understand and have treated dementia.
Have you taken her to the doctor about this? What does the doctor say? Has she had any memory testing? She might do better with an anti-anxiety medicine. It might calm her down some. I think I would start there. Best wishes...