Its a troubling situation, but lets look at some missing figures before commenting. In Canada the combined OAS/GIS is $1,344 if you don't get CPP or any other work pensions. Starting in July GIS will go up $947/year to bring her up to $1422/month, again assuming she's never worked so she doesn't get CPP. Why is it that she doesn't get CPP or at most a very small amount? The normal reason is a person didn't work or earned very little while working (part time jobs). Even Minimum wage (full time) will get 40% of the max CPP, this year that's another $3-4K (max is $12k). I assumed partial earnings and time off for child raising. If she had worked she would be up to $1,672/month, I propose that extra $372/month gets her into the rental market in most locales. Perhaps my math is off, feel free to fact check.
None of the above is judgment, its all just readily available figures (I use taxtips for my data). Below is my opinions.
I think there's parts of the story we aren't being made aware of, the numbers don't really match public data. This is a single person without dependents and no need for future savings. There is free medical care in Canada and seniors drug plans, no ranting about medical care. What happened that her payments are so low? Did she retire at 60 and get reduced payments? Did she have a divorce and lose her savings? Did she raise 4 kids without help? Why are seniors never expected to share housing but young people regularly get roommates? Why are her kids estranged and unwilling/unable to help?