If they sue your daughter and they are awarded judgments, only then can they garnish wages. The amount and how they do this varies by type of debt and what state the debtor lives in. There also will always be a garnishment hearing where the judge determines the amount. Your daughter may also want to keep bank accounts empty because creditors often go straight for those with no warning whatsover and freeze twice the amount owed.
Also, here is some information about garnishment procedures that you may find useful:
http://www.expert-credit-advice.com/wage_garnish.htm