I have to disagree with the interpretation you have given to the text...
First, her friend told her she is with a gringo...so your wife replied she is with another gringo, so it just means she is with a gringo TOO, just like her friend...not that she has another gringo besides you...
It does not mean she has another person, it is a way to interpret this situation and I don't think you should put your relation to risk just because of this note which is no proof whatsoever of what you may think.
