straypixelz9

If not in English, yes it needs translation but authentication or notarization not needed. Sounds like you lawyer is after some extra money based on your not familiarizing yourself enough with forms o procedures. Head up to guides above and read until you can recite all steps through naturalization. 

https://travel.state.gov/content/travel/en/us-visas/Visa-Reciprocity-and-Civil-Documents-by-Country/Guatemala.html
 

There is absolutely no requirement for a foreign marriage certificate be registered in the US....

Put yourself in the shoes of an officer......Recently married to a US citizen....no I-130 has been submitted yet..........she could be seen as wanting to get inside the US and remain..........to avoid the long spousal visa process..........a US spouse is a very strong tie to the US......

Don’t even think about not listing you in DS-160. 
With prior refusal, she’s probably better off just waiting for immigrant visa to go through. 

She has to mention you no matter what. Unfortunately, even if it is a red flag to her B2 filing. It sucks but she don't want a misrepresentation in her immigration history. Especially in this climate. Many people try to justify withholding vital information or lying to immigration because they think the opportunity is a valid reason to. But there is no justification. It is straight forward. She must list you.

No one here will tell you anything other than she must answer all questions truthfully, including questions about you.  Misrepresentation is a serious matter.

Your wife has been denied a B1/B2 tourist visa, so she knows that it asks about marital status and the name of the spouse on the DS-160.  There's no legal way for her to avoid mentioning you.