Mine drives a '11 Porsche Panamera v6...but it sounds like more than you want to spend tho. However it does allow me to have a great alternate driver especially when asked to chauffeur her around!
F10 is a great car tho! Maybe you could give her your 535i and get to upgrade to an M5!
'12 F10 550i (Dinan Stage 5/Intercoolers, CF Intake, Brace, Shockware, H&R Springs, Eisenmann Race Exhaust, CF rear difuser, Giovanni "Lindo" Graphite 20")
'10 e71 X6 35iDrive SAV (Space Gray) - Gone
'06 e85 Z4 M Roadster (Black Metallic) -Gone
'08 e92 M3 coupe (Sparkling Graphite) -Gone