Is it possible that someone else has already claimed her as a dependent? Does your daughter have income and might have already filed her own tax return without indicating that she could be claimed as a dependent on your return?
The above would be the most common explanations for an e-file rejection based on a dependent.
There is the ever-present possibility that someone else made a mistake and completed their return using your daughter's Social Security number.
The best course of action at this time is for your to print, sign, and file your tax return by mail. Causes for e-file rejection are not always reasons for the IRS to not process a return. Quite often, with a paper return in hand, the IRS can resolve a problem quickly and move on with issuing your refund, if one is due.