Since her return was Rejected, open it in TurboTax and change her Filing Status to Single and Efile again. This would be the easiest solution for you.
Since your return was already Accepted, it is easier to change her return. Technically, if you live together with your child, the one with the higher AGI (Adjusted Gross Income) should claim Head of Household.
Click the link for info on Tie Breaker Rules.
If you do want to Amend your Return, you have to mail in an Amended Return after you receive your refund. Your girl won't be able to Efile and claim your child as you have already done that and been Accepted, so her Efile would Reject. She would have to mail in her return.
Click the link for more info on How to Amend a 2018 Return.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
