What qualifies as a performing artist?

It depends, the combined adjusted gross income for both you and your spouse cannot exceed $16,000 before deducting the expenses. She has to have two employers in 2017.  Check below for all the requirements, hopefully you meet them.

You are considered a qualifying performing artist if you meet the following requirements:

 - Performed services in the performing arts as an employee for at least two employers during the tax year.
 - Received at least $200 in wages from each of the two employers.
 - Had allowable business expenses of more than 10% of gross income from the performing arts
 - Had an adjusted gross income of $16,000 or less before deducting these expenses.

In addition, if you're married, you must file a joint return with your spouse unless you lived apart for all of the 2017 tax year. If you file a joint return, you must figure the first three bullets above separately for both you and your spouse. The last bullet applies to the combined, adjusted gross income for both you and your spouse. These expenses are deductible whether or not you itemize deductions on your tax return for 2017.

There are no credits - only the advantage of being able to deduct your QPA expenses without having to itemize your deductions.

If you are eligible, navigate to Federal Taxes, Deductions & Credits, scroll down to Employment Expenses and click Start/(Update) next to "Job-Related Expenses". Proceed through the program prompts and enter your expenses. You will get to a screen Any special situations? to indicate that you are a QPA.

TurboTax will prepare a Form 2106 and include it in your return.

The AGI is the total for both spouses and includes all income sources to qualify for the deduction.  Here is the link for form 2106.  See page 4 of the instructions.