More important is the she OPT OUT of the advance payments so she doesn't get a shock on the 2021 return where she has to pay it back ... no double dipping on this credit will be allowed.
The Opt-out or "unenroll" portal seems to be live, but other promised functions ("enroll" and "update back account") have not been added yet.
https://www.irs.gov/credits-deductions/advance-child-tax-credit-payments-in-2021
