Sand is a generally crappy substrate. I don't know about the ruining of the pads, but I do know it can get in booklungs and cause problems, in theory. Also, the T can't do any burrowing in straight sand, more than likely.
Use good old sphagnum peat moss.. Everyone (including myself) seems to love it.
Just because your T doesn't burrow now, doesn't mean that it won't in the future. You might try explaining to your mother that sand could cause problems. If she's at all concerned with the welfare of the spider, she should understand at least partially.
Your Rosea would probably burrow if it had the correct substrate. You can use either peat moss or shredded coconut bark for substrate. I have heard of mixing sand and the above for the desert species, but Even my desert T's use the shredded coconut. The only thing I use straight sand for is my Bearded Dragon.