As has been mentioned, the anti-RFID wallets only block the tap-to-pay function type of theft, which doesn't seem terribly likely in your scenario. It's more common in major high traffic areas where it's easy to get close to people's wallets, and card skimmers and crooked clerks are still far more likely information breaches. It's possible even the doctor's office computers have been targeted - most older businesses don't tend to be as careful about securing their electronic files against theft as they should be. Or it could be an inside job, hard to say.
Do you know what the scammers used your mom's card to buy? Maybe it'd be possible to talk to the credit card company and set up some kind of extra security, particularly if your mom only uses it at certain stores or businesses. I know I've had to talk to a VISA person when making an unusually large purchase before.