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Be very careful with debt management companies (there are some legitimate non-profit businesses out there, most are affiliated with, or approved by, your state).
The FTC has a good set of resources to help you with debt management, see: http://www.consumer.ftc.gov/articles/0150-coping-debt
Quite bluntly though, in your sister's situation, she may be better off simply ignoring the debt (contact her creditors let them know that she has no assets and no income (her social security income is "exempt" they cannot collect against it), and that short of filing for bankruptcy protection, she is simply not going to be paying any further. The creditors may voluntarily "write off" the debt (this doesn't mean the debt goes away, it simply means they aren't trying to collect on it any longer).
If that doesn't work, or if they keep asking for money, she can send them this letter: http://www.rurallawcenter.org/docs/Getting%20Creditors%20to%20Cease%20Contact.pdf
Finally, if she wants to have the debt dealt with and over, she can consider filing for bankruptcy protection, but I would advise waiting for that until she is actually sued or they try collecting from her by wage garnishment or bank levies or some other more aggressive technique (saving bankruptcy for later in case she needs to use it for other debts). While you can file for bankruptcy protection without an attorney, see: http://www.uscourts.gov/services-forms/bankruptcy/filing-without-attorney, I highly recommend retaining a lawyer to do this, your sister will maximize her post-discharge financial picture if she retains a lawyer to do this for her and bankruptcy attorneys do not charge very much for their services).