We have a 2005 E53 Diesel which has had its share of little niggles, none of which were serious until a premature tranny failure - and even then it still got us home.

The only time we've been stuck was last weekend when the fuel pump relay failed 400km from home. Breakdown recovery gave my wife a loan car to get home and trailered the car to the dealer the next day. So I guess you can't really say she was stranded even then.

We do have a 3rd party warranty too which has saved some nasty expensive surprises.

It doesn't have Japanese reliability, but then you can look at what has happened to Toyota in the last 12 months and their recalls. BMW have never had anything that major. I suspect BMW's problems are the cars are hugely complex (same as Merc, Jaguar, Audi etc) and therefore tricky to fix without clever support technology. In my experience the costs have been higher to find the problem rather than fixing it. The fuel relay took 4 hours to find ($500) and $13 to fix as no fault codes were thrown.

In all honesty I wouldn't worry about it. If she's that concerned get her a good breakdown support cover.

__________________
Me:
Current: 2011 E71 40D Vermilion Red/Beige Nappa

Wifey:
Current: 2012 R80 Countryman SDX Green/Cream