I'm a poor old Mum with arthritis ..Lol ...you name it I've tried it .
It will soothe the joints but it's not a cure .I use some stuff called Pferdesalbe which I get in Germany ..it's a similar thing and much better IMHO than Emu oil.
You can buy it online
here
Although it's much cheaper for me as I have family who send it or I stock up when we go over.
There are lots of things you can do to help keep mobile with arthritis and ease the pain in your joints .Have a look
here
All the best to your Mum ..