Not understanding compound interest:
payment = PMT( rate, payments, amount)
payment = PMT(10.2/1200, 84,84000)
payment = $1,403.20
10.2% APR, is 10.2/1200 monthly rate
84 payments
$84,000 is probably the new vehicle + negative equity
If the original loan was 84,000 dollars, at 10.2% compounded monthly, after 36 payments she would have paid $50,400 in total, of which is $21,631.48 interest, $28,883.72 of principal, and owed $55,116.28.
Not saying she's not a financial idiot, just the numbers just don't add up.