She would have to file a federal amended tax return, Form 1040X, to change her dependency status. In TurboTax she would change that status in the Personal Info section for her name. See screenshot
See this TurboTax support FAQ for amending a 2016 return (desktop or online editions) - https://ttlc.intuit.com/questions/3061514-how-do-i-amend-a-2016-return-in-turbotax
An amended tax return can only be printed and mailed, it cannot be e-filed. The IRS will take 16 weeks or longer to process an amended tax return.
You can file your tax return with her as a dependent but you will not be able to e-file since a tax return claiming her personal exemption has already been accepted by the IRS. Your return will have to be printed and mailed.
