what to do?

85 year old lady, single (widowed, i think), seems in pretty good health for her age, has lived in this house for a long time, has been doing gardening there all that time, apparently at some point won 1st prize for that town's gardening contest. not too long ago had to have her german shepherd put down. got another one, 8 or 10 year old, from the shelter, because she doesnt think she has that much more to go...
has probably 14 cameras around the house, hooked up to 3 DVRs, figures somebody wants her house, and is trying to get her out of there, messing with her garden, trimming her hedge 6 inches lower than it used to be, taking chunks out of her trees, taking her garden stones - which she got for a fair bit of change (apparently stones are good in garden b/c they help retain moisture). she's had 2 security companies install the cameras and DVRs for her, but at least one of them seems to have been gouging her, and she doesnt wanna be involved with them anymore. she wants to get good footage of her neighbours coming into her backyard to steal her stones and damage her trees. she pretty sure the neighbours whose backyard is kitty-corner to hers have 3 cameras pointed at her house. either they are the police or they got some kinda deal with someone who's in the police, so she doesnt feel she can go to the police with this anymore. she's suspecting someone's been inside her house because she's heard ppl speaking upstairs where her DVRs are, and she suspects they took one of her harddrives out of one of her DVRs, and so now she's lost some valuable footage that would prove... i forget what.
she really wants me to help her out.
on the one hand, she's a customer, she wants a better view of a certain area, i suggested a different camera, she's all for it. with the missing footage, i told her likely one of the harddrives failed and thats why the footage is missing. i saw her receipt for the purchase of this DVR, it says 1 terabyte, the dvr says its got 500 gigs, it should still be under warranty from the company she bought it from, they should fix it for free - which i told her. there's probably some more work she'd have me do there.
on the other hand, as much as i am willing to entertain the idea that someone could be messing with her, damaging her garden, taking garden stones - more likely unrelated things than a concerted effort, i have a strong feeling that this lady is suffering from some senile dementia or something, suspecting that people are out to get her, to get her out of this house, because they want it, and they want it cheap, and she doesnt want to be pressured out of there just because she's an old, lone lady.
i dont want to feed her probable dementia, though i dont know whether anything i'd do would change things either way. i feel like doing this work she wants done is taking advantage of her, because its probably all in her head, and so she doesnt need to spend this money, and all the money she'd already spent getting ripped off by one of the previous security companies she dealt with. she seems aware that these things she says may sound crazy, but she doesnt think she is. she asked me something like "you dont think i'm crazy, do you?" to which i answered "no, not really". i've never really had to deal with this kind of thing. now i think i should have said how it all sounds, somehow try to tell her gently. hope that big friggin dog wouldnt freak out on me for upsetting his owner. but she's not crazy enough to be dangerous, so nobody can really step in and lock her up. nor should they - she's not doing any harm. just to herself. spending all this money and worrying that ppl are trying to screw her out of the house.
i dont want her to spend more money and persist in her paranoia. but if i walk away someone else will come in and gauge her again. and she really wants my help with the security setup. what to do?

its been bugging me. i keep trying to think it out, and what i got in my mind at the moment is to try to find some kind of volunteer senile/demented service to keep an eye on her, possibly take care of her somehow, if she's not far enough gone yet then when she does. this was phx' idea, which i like. but does such a service even exist? i also want to call her and tell her what i think of her situation, but ultimately say that if she wants, i can do some work for her, but i'm hoping she takes what i say into consideration, talks to her doctor about it, i dont know. is there even meds for this kind of thing? it seems obvious that her judgement is impaired, so how can i trust her judgement when i tell her what i think? but i dont think she's messed up enough for "the government" to step in. what to do?