What occurs in a wage ignment? ?

My aunt has just received a notice of intent to ign wages. Her husband was the one paying off the debt, but he recently ended up in jail. Now my aunt hasn't been paying the debt because she can't afford it alone. She is on the WIC program to provide her daughter with food and so be able to pay her bills. Is there anything she can do to prevent her wages from being igned? If not, what would happen if they were igned, is there a certain percentage of her wages that are igned? What should she do? Any advice and information is welcome. She lives in Illinois.