On thing to keep in mind is, if I remember correctly, she has another small child to support. If I am remembering that correctly she could ask for and win a variance in the basic child support figure by $50-$100 a month.
I would figure out what the monthly difference is between what the support would be using her wage from the w-2 and what the imputed amount would be (some states have a specific amount that is used based on age). It possible to get it imputed just on 40 hrs a week at her current wage.
I understand your frustration with the non reported wages. My ex has forever had an unliscened business that he made big bucks on, and asked for every little deduction from his CS based on his regular job.
I personally think that the CS tables here in WA are set a little too high, so I never really pursued his unreported wages.
How is your daughter doing? She has been in counseling for a few months at least now. How does the counselor say she's doing. Is her mother taking her anger out on her during visits? I would really love an update. Thanks!