I've banged on about cheque fraud on all the forums so won't bore you on here but basically, there's little she can now do. Police are the only hope.... ....cctv is a bit of a joke, unless the garage have lost money they're not interested and if they spot something associated with criminal activity guess what - they'll tell the police (who'll do not too much unfortunately).
Moral of story - ALWAYS release goods on the back of cleared funds. Best route is a chaps payment, same day, or a bacs payment (cleared in 3 days). But ONLY after the money is in your account. A bank draft is no safer than a cheque - even if you call the drawee bank and confirm it is genuine, one phonecall from the purchaser 2 mins after he has driven off in your car will cancel the draft.
Hope she gets some good news....