You will need to file a paper return because there is no way to get around the e-file system once your dependent has already filed and claimed themselves. Paper file your return with your dependent included.
This article will give instruction on how to print and mail your return.
Your dependent will need to amend their return to indicate someone else is claiming them.
See this TurboTax FAQ for help with amending.
You will need to file your return that claims her as a dependent by mail. Even if her return has since been amended, you are blocked from e-filing with her SSN on your return this year. Print, sign and date your return in ink, and mail it in. Sorry----this is a common problem for parents of teenagers and college students filing their own tax returns.
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as certified mail so you will know the IRS/state received the return.
Federal and state returns must be in separate envelopes and they are mailed to different addresses. Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.