Hi, I'd like to help you with your question.
It sounds like she could have schizophrenia and maybe be either need a medication change or may have gone off her medication. It is common for people with mental illness to feel fine on their medication and stop taking it because they feel they are better.
Another possibility could be that your neighbor is developing Alzheimer's. One of the first signs of Alzheimer's is changes in personality. Also, withdrawal from social and personal relationships.
Either way, it is unlikely she would try to harm anyone unless provoked. But if you do see her become more combative, contact the police. The police have the authority to place her in hospital care for an evaluation. Also, if you think you may run into her, try to have someone with you just in case. You or your neighbors may want to call your local community mental health center to ask what can be done. If she is willing to go for an evaluation, you may be able to try to get any family she has to take her. Or if she qualifies, she may also be able to get an in home evaluation by the local Area Agency on Aging. You can contact them to describe the problem and see what they advise.
All of these numbers and information can be found through the United Way.
I hope this has helped you,Kate