That is awful, so sorry for your family. Something similar happened with my grandmother which lead my mom and her sisters to get her checked out and eventually lead to a diagnosis of Alzheimer's.
As some one else said, this happens all the time. Not htat it makes it right or less infuriating(sp)..I would contact an elder abuse lawyer. I would look for an agency like "Pro Seniors" ~~ That is what it is called here. It is a lawyer service where they specialize in this type of crime. Also, if convicted the neighbor will be barred for life from working with any senior (at least in my state). It is a new law to prevent this from happening over and over again. Although it won't keep her from "helping" an elderly couple like she is now. But it will prevent her from fining a job in this market where she can continue to take advantage of the elderly. I would call an attorney TODAY! I am so sorry
I cannot imagine what Jane feels like. What a slap in her face after all she has done. I have no words except I hope she peruses legal action against the neighbor.