If I was your dad and expected to pay to maintain either car, I would slap you upside the head and go buy you a Yugo and tell you to get a job (yes, Yugos break more often but the average repair costs a lot less than $1500). So I can't blame your mom for being pissed.
The Mercedes 560Sels are kind of larger cars but don't even have that much room in them (ok, next to nothing to be completely honest) next to some of the cars I've owned...
your mom is obviously retarded because just because the car is big doesn't mean that the seat or the pedals or the dash are going to be any different its just harder to minouver around