How to find out if NATO 2 VISA is still valid?

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Trying to help a friend with some issues regarding the validity of her US NATO 2 VISA.

The question is how can she find out if her VISA is still valid for re-entry to the US? She is currently in Germany. She's called the US Consolate but they can't seem to verify if her current VISA is still valid and she's basically getting the run around. Can anyone help by either providing a website or phone number to check if she can return to the US? Her VISA is multiple entry and is NOT expired.

Background/Long Form: Her husband (employed by the German Armed Forces in the US) sent her back to Germany and stated that he would be filing for divorce in Germany. She doesn't want to wait the 1 year separation time required for divorces in Germany so she would like to come back to the US to get divorced (6 months) then file to have the German courts recognize the divorce. Her husband doesn't want her to come back to the US as he has already started seeing another woman but that's a whole other story; he doesn't want to file here as he may be looking to pay a hefty alimony check.

She wants to come back, discuss the separation and divorce proceedings and move on with her life. Even though her physical VISA is still valid she would hate to fly to the US only to be turned away and waste the money. Any help would be greatly appreciated.