Car accident - Diminished value claim

Is anyone familiar with a diminished value claim?

Wifes car was parked in our building and someone hit her at night and left a card, their insurance (progressive) is paying the $9k in repairs, we are seeking diminished value but progressive is telling us to "prove our case" for value. 

kind of difficult to prove ..

diminished value is designed to pay owners for the value their vehicle MAY lose due to being in an accident.

I say its hard to prove because you technically didn't lose any value, and will only lose value if you decide to trade the vehicle in (dealers will attempt to low ball you because its been in a accident, even though it was fully repaired).

so your trying to recover for a loss you didn't incur and may never incur

To prove your claim:

1. determine actual cash value of said veh
2. determine trade in value of veh
3. provide repair estimate
4. cross fingers and hope insurance company is loose with the fund$
 

.