shame you can't get hold of some tomcats wee and leave it there for a while (no idea how you'd do that though!) that would make her look somewhere else. That's the most effective method, but hardly practical.
You could try distraction or deterrent. Wait for her to start sniffing the rug and make a loud noise (shout/clap) or use a water pistol (you'll only need to use it once!) to distract kitty and make them associate the nasty noise/result with the sniffing of the rug.
We had a cat who would always go on our rug, it was only the rug he'd go on, but once he'd gone on it, he wouldn't bloody stop. The way we stopped him was to put a clean litter tray right next to the rug. It was in the living room for a few days (we had to move it out if anyone visited) but it worked. Also spraying the rug with something that smells of orange (make sure it doesn't stain first). Most cats hate orange. Failing that get some shake n vac or talc/baby powder and spread it all over the rug, quite thickly. The powder will stop the cat going on the rug and you can hoover it off after a while and it makes the rug smell nice too - 2 birds, one stone!
Does she have a litter tray inside the house? Is it clean? Sometimes, fussy cats go on fabric because it soaks up and if they have to go somewhere else, make sure they have somewhere they can go where the pee won't end up going on their feet. They have to clean their feet with their mouth, so obviously, they're going to go somewhere that they can keep their feet pee free!!
Alternatively, kitty could be missing your mum, and it might just stop when she comes back. Used to happen when my parents went away and I was home with the kitties.
Good luck
