You do not need to wait for her amended 2019 return to be processed, before filing her 2020 return, particularly if the amendment didn't really change anything (apparently your case). Assume the amendment is correct.
In the interview, when TurboTax (TT) presents your capital loss carry forward calculation, if gives you the option to change it, if your records show a different amount.
If your student was your dependent any of those years, she does not get the full standard deduction (~ $6300 for 2017 and earlier and ~12,000 for 2018-20). Her standard deduction is limited to ~$1100 or her earned income +$350. If she had other unearned income, including taxable 529 plan distributions, her capital loss carry forward will be reduced, each year.
Even if she was not a dependent, she is required to reduce her other income by the capital loss before applying her exemption amount (~$4000) for years before 2018.
