I think I would call my MP's office if I was in your situation. Perhaps time to reach for some support from your government representative,
your Member of Parliament.
Immigration lawyers are expensive, I don't know if you want to consider one, and whether they would help, but if I were in your position
I would be considering whether there is expert legal advice available, and, reaching out for support though my MP. Perhaps the MP can check with Immigration and give you more information as to why your g/mothers applications are rejected and what it would take to get approved.
I wish you Good Luck.