Does your contract have an acceleration clause? In other words, does the contract say that the balance becomes due and payable on default? If it doesn't you'll only be able to sue her for the payments that she has missed which is not the $890 balance but only a part of it. You'll have to wait until the contract term ends to sue for the whole thing.

If you can confirm that the car has a blown engine I would caution against a repo because it would cost you for a tow and you'll probably only be able to scrap it for a couple of hundred bucks or pay a couple of thousand for an engine replacement.

But if she's lying and the car is still in good driving condition you ought to be able to sell it for a couple of thousand but then you only get to keep your $890 balance plus whatever costs you incur and you'd have to give her the rest of the money that you get on the sale.

There might be other complications under your state's repo laws. Here's a brief summary.

http://www.quickrepo.com/repo-compan...on-laws/nv.htm

What you do is up to you but you might consider simplifying your life by waiting until October and then suing in small claims court for the balance.