Every year I help my daughter prepare her tax return. This is the first year that I have used the online service. I have been unable to start a return for her.

Online is only good for one return per account. But you can use the same email address for 5 accounts. Online is only good for 1 return per account. So don't use your account or you will overwrite your return.

Sign up and start a new account here,
https://turbotax.intuit.com/personal-taxes/online

Then if you have her 2022 return on your computer you can transfer it into the Online version.  How to Transfer into the Online version
https://ttlc.intuit.com/turbotax-support/en-us/help-article/import-export-data-files/transfer-last-year-return-turbotax-online/L279eUvY2_US_en_US?uid=l8w7nlbv