Dependents are entered or deleted in MY INFO. If you already e-filed an accepted return that claimed the children, her attempts to e-file will be rejected even after you amend. She will have to file her return that claims the children by mail, or she can seek an IP PIN and try to e-file. Waiting for you to amend will not help her.
For the ex-spouse whose e-file is rejected:
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.**