She is widowed, in her early 80s, and doesn't have a lot of money. I suspect it's keep this vehicle going, or do without.
Kal Tire quoted C$1000 all-in (mounting/balancing/new valve stems/eco fee/taxes) for four all-weather tires (i.e. winter-rated).
It does drive well, and the rust appears to be mostly cosmetic. If the paint weren't so bad, it would look a lot better.
I wonder whether it originally came from a place with intense sun exposure? The peeling clear coat and faded paint look like old vehicles seen in Colorado.
Do you have a Walmart that does tires nearby?

Because they have these all-weather tires for $154 each, so probably $700 for a set of four installed.
Blackcircles has Imperial all-weather tires for a similar price, and it works like Tire Rack