Thank you @Mike E I suspected the same too, about the clock resetting to 2020.
I am also trying to gather more info from my friend (let's call her Jane D) who is in this situation. I am not sure and highly doubt an adoption was made by the U.S. citizen [stepmother]. The stepmother was married to Jane D's father for several years and lived with him [and raised Jane D] in ForeignCountry before returning to the U.S. and later [amicably] divorcing Jane D's father. Jane D's father was not interested in and did not seek U.S. LPRncy or naturalization.
After divorcement, they remained close and the stepmother returned to the U.S. with Jane D when she was well below 10 years old, for about 1.5 years. However, Jane D returned to NativeCountry and completed education up to high school there, before coming back to the U.S. to live with her stepmom and attend University [in 2020].