Marriage between filipina and filipino

SIR, please help naman.what do we do need to do if my sister want to use her surname po nung di pa sya kasal. Shes married to a US citizen, they got married here in the philippines. Then after that they stayed in US, unfortunately, now, they were separated already, because the Foreign guy FILED A divorce or annulment in that country and a decree is validly obtain. Now my sister, stayed there despite of the fact that they were separated already, she work there for years and she's now a green cardholder.ngayon, gamit nya yung apilyido nya nung dalaga pa sya sa mga papers nya dun sa US,. Then she decided to go back here in the philippines, para machange nya lhat papers nya sa apilyido nya nung dalaga pa sya tska passport nya at sa NSO, kasi daw even their married was annulled in another country, here in our country it is still recognized na married pdin sya. Thanks. Help nmn what domwe need to do po?

Marriage between filipina and american citizen sorry , dont know how to edit it heheh thanks