I'd be careful, she probably thinks you have a green card. sounds stupid I know.. you should go to their website and get the official word. Some nationals of certain countries require a special Visa that could take up to 2 months to get.
URGENT NOTICE
As of September 14, 2001, the citizens of the following countries willing to travel to Mexico for any reason, without a Green Card in the United States, will require previous approval from the Mexican Immigration Authority (Instituto Nacional de Migración), in order to be able to enter Mexico.
These countries are:
Afghanistan Albania Angola Argelia
Argelina Rep. Armenia Azerbaidzhan Bahrein
Bangladesh Bielarus Bosnia-Herzegovina Comboya
Congo Croacia Egypt Estonia
Georgia Haiti India Irak
Iran Jordan Kazajstan Kiguistan
Latvia Liberia Lybia Letonia
Libanon Lithuania Macedonia Marruecos
Mauritania Moldova Mongolia Nigeria
North Korea Oman Pakistan Palestina
Qatar Rusia Saharaui Rep. Saudi Arabia
Serbia y Montenegro Siria Somalia Sri Lanka
Stateless Sudan Tadzhikistan Tunez
Turkmenistan Turquia Ucrania United Arab Emirates
Uzbekistan Vietnam Yemen Colombia
Cuba
In order to get this approval, they should submit, in person, the documents required, as posted in our web site. The process for requesting this approval, will take four weeks and it will be done through this Consulate, except in those cases when the petitioner has a business or personal contact in Mexico, in which case it has to be done directly through the Ministry of the Interior (Mexican Inmigration Institute).
The contact information for the INM is as follows:
Instituto Nacional de Migración