QUOTE
Translations: All documents not in English, or in the official language of the country in which the application of a visa is being made, must be accompanied by a certified English translation.
http://caracas.usembassy.gov/wwwh2469.htmlSpanish is the official language in the country where the beneficiary is applying for the visa. The approval from USCIS allows the beneficiary to apply for the visa, showing that she meets the requirements to do so (you've met within the past 2 years, you're both free to marry, etc.), but it is not the application itself.
Also, if that sentence means that the language in the country in which the application is being made is English (the U.S. - if you assume the USCIS stage is the actual application - and it is my understanding that it is not -, then it'd read "All documents not in English, or in English (the official language in which the application is being made), must be accompanied by a certified English translation." - it doesn't make sense.