As Champ @Bsch4477 suggests, one remedy is to file your return by mail. The IRS does not reject mailed returns. They will process the mailed return that claims your grand child and sort out the duplicate use of her SSN. Someone will face repayment of child-related credits they were not entitled to receive.
Another possibility:
GET IP pin in order to e-file if your dependent’s SSN was claimed on another return
https://www.irs.gov/newsroom/irs-takes-steps-to-help-prevent-refund-delays-by-accepting-duplicate-de...
https://www.irs.gov/identity-theft-fraud-scams/get-an-identity-protection-pin
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
