Technically she is not entitled to the benefit of a marriage that never existed.
However if she entered into the marriage in good faith and the marriage was annuled before she received her permanent green card, she could have obtained a waiver based on the annulment.
At this point her challenge will resurface when she applies for citizenship and USCIS decides to investigate.
It is advisable to contact an immigration lawyer to ensure there are no fraud issues.
You are welcome to use the link provided below.