Her citizen is going to be revoked by USCIS. Based on your own post, she divorced him while she was in the process of procuring her citizenship. However, all of what I just said can be null and void under one condition, she applied for her citizenship under a 5 year rule, NOT 3 year rule. If her naturalization was based on marriage to a US citizen, which is 3 year rule, then the law requires that she be married and living with the same US citizen until she is sworn-in as a US citizen.
Let us use this scenario: Your soon to be wife, married her ex-husband on Jan 1, 2006 and her green card was approved on June 1, 2006. While her naturalization application was going through the system (she applied on Jan 5, 2009), she filed for divorce on July 1, 2009 and had her naturalization interview was on July 2nd, 2009. On the day she filed a divorce and her husband was served of those papers, she was required by law to notify USCIS on her change in marital status during her naturalization interview. Let us say she was sworn-in as a US citizen on August 1, 2009, she committed multiple perjuries as she needed to indicate on the Form N445 of change in her marital status. Assuming USCIS never found this during the latter part of her naturalization process, this will be time for them to find out and it won't be pretty for her and you. She will be required to attach her divorce decree to the forms filed, because she will indicate she is divorced.