We not allowed anymore.
But I do think a lot of issues can be solved by doing a complete consultation and working out why the client has bad skin on their heels.
As this is your mom, I sure you know her very well.
The reason we don't use a blade is it creates trauma and the skin reacts by producing more thicker skin quicker. Similar concept to clients with oily skin who over wash and scrub their faces.
Lots factors like open shoes , working in aircon, standing all day , hormones, sugar level, diabetic, weight issues, back issues, medications.
I found best for my clients who are older is the callus peel, I use mediheel peel as I prefer it. But it really helps with clients who are prone to thicker or even flakey skins and you don't run the risk of injuring them with aggressive foot files.
Follow up with a nice foot mask and massage can also really help.
Your mom should try applying foot cream in the evenings if possible to help avoid building up so quickly again.