I test drove a 2005 Mini Cooper S for about 45 minutes. Absolute Hoot. 6speed manual. Sports suspension. Rocked! I did 2-3 trips through a highway cloverleaf and just played with the trottle to get the car to rotate. Lots of fun. A bit "buzzy" at higway speeds, but it is a 1.6l so, give it a break!
Not sure how old your sis is or how much insurance might run for an S, but it took my "better half" to convince me that 2 car seats would be easier to access in a sedan and not a tiny hatch, or I would have bought one