Was the marriage annulled, or divorced? If it was legally annulled, it is generally treated as if it never happened.
See a lawyer about this ... if you are not married at the time of adjudication, I am not so sure that you are ineligible for the green card even though there was a marriage in the past. The lawyer should be able to clarify the rules and how they relate to your specific case ... when you got married, when you got divorced/annulled, when your case was approved, etc. Ask your mother to contact a US-based immigration lawyer and arrange a phone consultation.