"Are you saying even if she withdraws 2021 contributions and earnings in 2023, it must be reported on 2021 returns?"

Excess in 2021 means 6% excise tax on the disallowed contribution for each year it remains in the account. That means 2021 and 2022.

There is tax on the attributable earnings.

There is an early withdrawal penalty if the person is under 59 1/2.

For each and every year until the excess is either absorbed (carry forwards can be treated as a contribution for that next year, but your taxpayer still didn't qualify...) or removed. That means the year of removal saves the excise tax.

"Since her 2021 ineligible contribution was not withdrawn by December 2022"

By tax return filing due date, including allowable extensions...

"does she owe penalties for 2022 as well?"

Yes.

"What is the deadline to withdraw that 2021 contribution without 2022 penalties - was it December 31, 2022 or April 18, 2023 ( the 2022 tax return due date) ?"

April filing due date, 2022 (timely filing of tax year 2021 info)

or

October 2022 <== extension, if applied for, creates a later due date

"If you don't remove your excess contribution before the tax deadline, you can file an amended tax return after you've removed the funds, but you must do this by the October tax extension deadline. The government will review this and refund you any penalties it's taken out if necessary."

https://www.fool.com/retirement/plans/roth-ira/excess-contribution/

I also like investopedia articles. All of these are geared toward the consumer trying to figure out their options, so they are easier to read through than the IRS pubs:

https://www.investopedia.com/what-to-do-if-you-contribute-too-much-to-your-roth-ira-4770686

https://www.investopedia.com/articles/retirement/04/042804.asp

"Edit: Two tax professionals said - you do NOT amend. When she withdraws this year, she will get a 1099-R for the withdrawal, and then you reconcile it for the 2023 return."

Did she report the tax and penalty on the 2021 tax return, for the excise and the taxable earnings? I thought you stated no. Here's what you are overlooking:

Each tax year has a Status. that you need to address That is Excess (subject to excise tax because it was left in the account for that tax year) and any taxable earnings (because you are not allowed to benefit  from Roth tax-free rules on disallowed funds).