Well, she don't have an excess, so she's probably better off driving the car until it breaks then making the insurance pay the repairs as it would be classed as an accident?!
i think your barking up the wrong tree budy...
your getting confused between warranty and insurance.
2 completeley different things.
the cars servicig is your responsibilty and thats it really if you have a car you should expect to pay for these items as they are wear and tear items.
get them to take car to garage that should be coverd on your breakdown then your mum will have to pay for new belt to be fitted.
p.s are you sure its timing belt and not just an aux belt big difference in these