I don't think she has mental health issues. She's really a very nice lady, and she relies very much on her church for emotional and other support. We try and help with her gardening and what-not, but the church is giving her a lot of help. TBH, I don't know whether it was a preacher who told her this, or just somebody at the church. The church seems a little 'out there' by British standards, at least, but I think they're good people.
I see her reaction in much the same way as I saw my dad's reaction to people coming to the door asking for donations. As he got older, he became less able to distinguish between genuine charities and the less genuine variety. I'd go as far as to say that genuine charities knocking on doors asking the very elderly for money gets pretty questionable, but that's another issue.