Before you consider going to the courts, how long did she have the car for before getting the clutch replaced in May.
Different cars have different driving styles and can take some getting use to.
Did you or your dad notice anything wrong when you both drove the car. Before smoke starts billowing out from the gearbox/bonnet, you would notice a horrendous smell of burning.
I have replace the clutch once on my car with over 100k on the clock, Yet, loaned it to my mother for a weekend, also driving over 40 years and it came back with an awful smell of clutch burn.
You can burn a clutch out in days. If you Mother has had the car for years previously without issues, then there is a problem here.
What I would do is, have the clutch replaced at another garage, having the car and worn parts inspected by an independent assessor. Depending on the outcome, then head to the courts for full reimbursement of all costs.