Only one person can claim the Child and Dependent Care Credit. If you lived together, and she is claiming your daughter as a dependent, only she can claim this credit. If this is your situation, since your return has been accepted (with incorrect information), then you will need to amend your return (because you cannot claim the credit), and she will have to mail in her return; or, alternatively, e-file without the credit and then mail in an amended return claiming the credit.
However, if the situation is that you live apart and you are the Custodial Parent (the one with whom the child lived the longest and for at least 6 months and one day of the year), then only you can claim the Child and Dependent Care Credit (as well as Earned Income Credit). She would need to state that you are granting her claim of her daughter as a Dependent for limited benefits, which is her exemption and the Child Tax (and Additional Child Tax) Credit.
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