That depends hugely on 1) what the car is actually worth and 2) how the dealership wants to structure the deal. As I suspect you know, car dealerships are notoriously crafty when it comes to setting up the sales, especially when a trade-in is involved.
Hypothetically, if the car is worth about $15,000 and she owes $11,000, she should net about $4,000 from trading in her car. The dealership would pay off the creditor on that car and then put the $4,000 towards her purchase of the new car, leaving her about $2,000 to $3,000 to finance.
This is, of course, an overly simplistic hypothetical. You also need to consider tax, tags and title costs.
Also, several customers have asked how they may direct a question to me in particular. If you specifically want me to assist you in your legal matter, just put "FOR JOSEPH" in the subject line and I will gladly pick up the question as soon as I am on-line.