They would not be taking your whole check...only 15% which would be $120 per month. It really doesnt matter if you work part time, your wages are garnishable. To avoid garnishment you MUST enter into voluntary repayment. If they have sent you the pre garnishment 30 day notice, you must respond within that 30 days.
If you are not in repayment, your taxes will be taken. Taxes being taken are not considered being in repayment but a federal seizure. They can still garnish you
and take your taxes. Did the CA send a warning notice on behalf of the guarantor or was the letter directly from your guarantor?
Sounds like the collector was doing exactly what she was suppose to be doing.