Under your description, the embryo donor might have French nationality, since at least one of her parent was presumptively a French citizen, but since she was born in the US, it was also required that the birth was recorded in the French civil register, so one might have to litigate to get the donor's French citizenship recognized. There is a time limit under the French Civil code Art 30-3 (probably not applicable)
When a person habitually resides or has resided in a foreign country,
in which the ancestors from whom he holds the nationality by parentage
have settled for more than half a century, that person may not prove
that he has the French nationality by parentage if he himself or his
father or mother who could have transmitted it to him has not enjoyed
the possession of being a French national. In that event, the court
must record the loss of the French nationality under Article 23-6
A complication is that surrogacy is illegal in France, and requests for the appropriate certification from the French government may be denied, as stated in the article "In the majority
of cases, children born abroad by surrogacy are denied
French civil status, and there are delays in the issuing of
certificates of French nationality". This being a political matter, it could change. A further complication is that in the US there is significant variation between states in whether the donor is on the birth certificate at all.