US citizen with foreign parents

I am a U.S citizen but my mother is a Salvadoran National with a U.S green card. I am planning to go to China as a tourist but I want her to come along and enjoy the trip with me. Does she have to apply for a Visa back in Central America or can she go to my nearest Embassy(New York). Also what would be the requirements for her to obtain it, would it be the same as a Mexican citizen?