@ossobuco,
I just fully read that coyote link; they would be on your sister's side.
Me, I remember our cats loving going outside, and they didn't roam.
I know feral and maybe other cats do.
Somewhere here there is a thread about this subject (well, probably several). I remember posting an article that showed how you can have a cat track outdoors, so it can spend time under or near the trees without being prey, or, the alternative, predators. I picture the set up in that article as attached to the house fairly high up - which didn't appeal at all to me, but the idea was interesting.
Maybe there is some possible adjustment by both women - build an area into a chain link and topped enclosure (maybe topped with a wire mesh over 2 x 4s) with some nice things in it like a little hut with cushions, water availability, food dishes?, toys? perhaps grow some catnip plants and/or catmint; perhaps the whole thing by a pretty tree. I have no idea if that would work, as we never considered doing that, and, to me, your mother shouldn't have to. I bring it up relative to possible peace keeping.