If reliability is a factor, there's a good chance Fiat won't lose out to MINI. MINI was dead last this year in dependability. I'm going to go ahead and doubt that Fiat will be worse. As mentioned before, I'd wait for the Abarth which at least isn't potentially dangerously slow. Also, for how slow it is, there are other cars which get better mileage.
However, in the end, it's up to her and she needs to get seat time in both.