Married in Mexico Divorcing in States

I have a friend who wants a divorce from someone she married in Mexico. I’m not sure if they were citizens when they married in Mexico. How she obtain a divorce? Does she have to divorce in Mexico?

If the marriage was made official in the US she can obtain a divorce in her state of residence, based on the applicable laws there. If the divorce was not recognized by the US she will need to speak with an attorney in Mexico to determine what needs to be done.