Make sure there is no pre-payment penalty as some loans have been sneaking that back in.
I don't know what her scores could be but maybe opening a secured card or making her an authorized user on one of your cards (you need not give her possession of the card) can boost her scores significantly in a very short period of time.
The 2 things to look out for refinacing are
1) what is the loan to value - I think you are OK there putting $2,000 down on a $6,800 car but you never know without looking at NADA values. Most lender will loan up to 110% - 120% of the NADA value. With a high interest rate over 5 years you won't be paying down too much each month at first and the car will continue to depreciate.
2) the age and mileage of the car at $6,800 its definitely a used car with some years and miles under it's belt. Many lender limit how old or how many miles can be on a car.
If she has a relationship with PNC maybe she can ask them what her chances are, what particular score they use and other factors so she can know before wasting a hard inquiry although if done in a short period of time they are really grouped as one inquiry so there is little harm in applying now.