A friend of mine came to the States on a K1 visa, adjusted her status and received her green card. Unfortunately her marriage did not work and she left the US to go back to her home country. She is filing for divorce.

She could have applied to remove her conditional status starting May 1st, which she obviously is not interested in doing. However she has made friends in the US during her time here, and would like to be able to visit them later in the year. She wants to be "clean" with the immigration so she'll have no problem coming back to the US on vacation. What does she need to do though? I could not advise her at all and feel kind of helpless. Does anybody know who she should contact to let the USCIS know that she has left the country and will not pursue her immigration journey? Will she have problems re-entering the US if she does not notify anyone?

Please help! Thanks.

M.

As far as I know, she shouldn't have any problems later on. She would visit the US on a visitors visa or if possible, VWP.
I had a coworker in Germany who was married to a USC, she used to have a greencard but never got it renewed. She travelled to the US without problems but I don't know if she was still able to use the VWP or if she had to apply for a visitor visa.

She can formally relinquish her green card, by filing form I-407

http://london.usembassy.gov/dhs/forms/I-407.pdf