https://www.taxtools.com/products_tt.aspx has some real good Q&A flowcharts to help answer some of these "basic" questions that often seem to confound EVEN ME! IRS has the same sheets, but harder to find.
https://www.irs.gov/help/ita/whom-may-i-claim-as-a-dependent
https://www.irs.gov/credits-deductions/individuals/earned-income-tax-credit-eitc
You have all the information, which you have not shared with us. Do your homework and work through this problem. If you get hung up, come back with the results you are having problems with and the detail aspects that seem to cause the problem.
Earn your fee or send the client off to a VITA program - They do this all day long.