This is your wife's fault 110%.
She hit a parked car, it really doesn't matter (much) that his mirror was sticking out. There's no way his insurance is just going to pay out on it, you'll have to take him (them) to court, with pics, and hope the judge decides in your favor (unlikely).
This is correct. If you hit a stationary vehicle - it is always the driver's fault.
The parked vehicle may have been parked carelessly - but it doesn't matter how badly parked a vehicle is - a stationary obstruction is always avoidable, if a car is being driven in a manner appropriate to the conditions.
The point is that the collision as described is 100% your wife's fault. That's not to say that the truck owner shouldn't get cited for illegal parking - he should. But, a careful driver would always have been able to avoid the mirror - and that's the important bit.
