I would take it to the BMW dealer for an inspection (for a fee).. they will let you know what's wrong with it in written form, it could work in your favor since she said there was no mechanical issues. Good luck and post some pics.
'07 Audi A8 (w/ 20,000 miles)
'03 745Li (sold)
'03 Acura TL-S
'02 Infiniti QX4 (sold & new owner totaled it 4 hours later)