She might be better off putting a toilet and a shower in it and renting it out...
Does she still owe on the SUV? If so, is she upside down?
Most times you can get better money from your vehicle if you sell it, then purchase another.
If her SUV is paid off then she she shouldn’t have any problems trading in anywhere, but they will give her less than she could sell it for.
Also, if she still owes money... there have been reports of the car not being paid off by a dealer and the owner gets nailed for it. Or they’ll pay it off, but you will refinance any negative equity you had along with your new car.