I am aware that Jehovah Witness people have been stopping by and visiting with my Mom, on a regular basis. Mom (and Dad) raised us Catholic I am concerned that the J. W.'s are aware of Mom's failing mind, and are after her money. What, if anything, can I do, to protect Her?
An elderly lady of failing powers who is answering the door to callers is vulnerable to exploitation and criminality of all kinds; and threatening JW's is not going to solve the problem. Revising her access to cash and bank accounts and making sure that these are secure is called for. Along with sticking a big notice on the inside of the door reminding her not to open it to unidentified, unauthorised visitors - your local police may be able to provide you with useful material for this.
And yes the question is 8 years old but the problem seems to be eternal :)
Her "failing mind" is only going to get worse.
The following day we had a social worker and chaplain meet with her alone and let her decide without anyone coercing her. She put only her granddaughter, whom she lives with. After the social worker left, they went right back up to her room. Of course, we have to redo her will and financial power of attorney also as we don't know what else they could have had her sign.
A "no solicitation" sign is useful also.
My next door neighbors are an elderly couple (wife has dementia and husband is WC bound post stroke). Their 2 sons never visit (although they live very close). Anyway . . . I make a point of making sure the CNAs know I know them and I wander on over if I see a stranger at the door. OKAY, I know, I have enough to worry about at my own home but some bad ppl really will take advantage of vulnerable adults and we have to be vigilant.
Good luck to a fellow Catholic!