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There is a wide variety of things you can do, but the exact plan depends on how things "play out" and on what she purports to be the basis for her claims. You also have to consider that she may attempt to pass the blame to your mother at some point since she is the one who would actually have had to request that the police pursue you.
As you mention, defamation/slander/libel are all possible. In addition, there are specific cause of action for Intentional/Negligent Infliction of Emotional Distress (which can be called by some other names as well) and potentially for some form of harassment. Those are the civil causes of action that are readily apparent from the fact although it is quite possible that others may develop later. When choosing your attorney try and find one that does civil litigation as well as criminal defense so that they will know how to use both cases (civil and criminal) to set things up in the other case.
There could also, potentially, be criminal charges against her. This is really, really fact intensive but there could be some type of elderly abuse if she forced your mother into this although it would be hard to prove. There is also the potential for a charge of filing a false report.
PLease ask any follow up questions in this thread.