In tax year 2015 the gross income to be claimed as dependent under the Quailfiying Relative rules had to be less than $4,000 (Social Security does not count for gross income). If her gross income was over that amount then you should have not claimed her as your dependent.
You will need to remove her as your dependent and change your filing status to Single if you are not married and have no other dependents to claim on the 2015 tax return. You will need to amend the 2015 tax return using Form 1040X.
See this TurboTax support FAQ for amending a 2015 tax return originally completed using TurboTax (online or desktop) - https://ttlc.intuit.com/questions/3410543-how-do-i-amend-change-or-correct-a-2015-return-in-turbotax
An amended tax return can only be printed and mailed, it cannot be e-filed. It will take the IRS about 16 weeks or longer to process an amended tax return.
You will pay any taxes owed on the amended return by including a check for the amount owed with the mailed amended tax return. The IRS will send you a bill in the mail after they process the amended return for any interest or penalties owed.
To be a Qualifying Relative -
1. The person cannot be your qualifying child or the qualifying child of any other taxpayer. A child is not the qualifying child of any other taxpayer if the child's parent (or any other person for whom the child is defined as a qualifying child) is not required to file an income tax return or files an income tax return only to get a refund on income tax withheld.
2. The person either (a) must be related to you or (b) must live with you all year as a member of your household.
3. The person's gross income for the year must be less than $4,000 (social security does not count) in 2015
4. You must provide more than half of the person's total support for the year.
5. The person must be a U.S. citizen or a U.S., Canada, or Mexico resident for some part of the year.
6. The person must not file a joint return with their spouse.
