You can save about 75% by learning to do it yourself. I realize that's probably easier said than done, but the tools you need are very basic.

sorry for being technical, but i don't think the brakes have anything to do with the parking brake (i assume you mean the hand brake). that is applied using a cable from the handle to the back wheels. adjusting it or even maybe replacing it wouldn't be considered as breaking the bank. your mother doesn't seem to be the most skilled of drivers. i wouldn't trust her behind the wheel.

Tell her she is not allowed to use the car.

Let her know she'll need to spend HER tax refund on the brakes, and take the keys back.

Ouch I can feel your car's pain. This is why I don't let others drive my car. it's Bae

Since the parking brake isn't connected to any other part of the braking system then you'll only have to replace those brakes, not all of them. Shouldn't be to expensive. Might have some money left over.

Because no one here seems to understand: the parking brake, can be applied with a hand lever, or a foot pedal on some vehicles. It is a cable operated system, that manually applies the vehicle's regular front or rear brakes (depending on the individual vehicle) you can in theory ruin a set of pads if you repeatedly drive with the parking brake engaged, but for most vehicles that's only $80 or so for parts. Labor I wouldn't know.

Doesn't a warning light and beep come on if you do this? How does she keep driving without noticing this?

**** her

She should have to buy you the new brakes