First off, I've no idea how hard you have to press the brake pedal in a VW Up. However I have a non servoed sports car and latterly, people keep retro-fitting one to these cars. Expection of pedal pressure is less it seems these days.

Many moons ago, I had a hire car where the clutch pedal pressure needed was so little I was convinced at first push that I wasn't doing anything and was very cautious with my first gear lever push. So cars do vary to great degree.

The sensible thing to do is visit the dealer, surely they have one she can try, that sort of thing can usually be compared quickly in the car park. I have known a servo fail in an older car, and it's a huge increase in effort but my feeling is there is nothing wrong with the car and her last car just had a lighter touch/more servo action.

If your vacuum servo fails completely, you'll know about it. You'll be pressing the brake pedal so hard you'll be worried about breaking the bracket.

In general, heavy clutches and brake pedals easier to live with than light ones once you've got used to them. they're less fatiguing.