When researching La Malinche there are basically only three principal sources:
‘The True History of the Conquest of Mexico’ by Bernal Diaz
Cortés’ Five Letters to the King of Spain
‘The Aztecs speak – an Aztec account of the Conquest of Mexico’ taken from the Codex Florentino.
To a much lesser extent there is Francisco de Gomara’s biography of Cortés, which by most scholars is considered extremely flawed..
Each of these sources has its issues.
The Codex Florentino is actually a translation of Aztec hieroglyphics (they had no written language) by Spanish monks and as such may have extensive errors in meaning, although most of this account corresponds closely to the account by Diaz. A thorough reading of this document would also lead one to believe it is often exaggerated, so taking a grain of salt with it is advisable.
It must be remembered that the letters from Cortés to his king were clearly designed to laud himself and flatter the king at the same time. Cortés was in a bitter battle to control New Spain or Mexico over the objections and greed of the Cuban governor Diego Velasquez and so much of what he writes while similar in timeline at least may have embellished some events while omitting others.
Bernal Diaz leaves us with the most complete historical document, but clearly it was written by a naive man some fifty years after the events took place, and appears to view those events from hindsight through rose colored glasses. However, reading between the lines and ignoring some outrageous remarks, this document mostly rings true. The fact that Diaz goes out of his way to call out glaring errors by Gomara, also tends to diminish that work to the point it cannot be taken seriously. But most importantly, Diaz was an eyewitness and participant in the Conquest, and knew both Cortés and La Malinche (Dona Marina / Malinalli) personally so his account must take weight over the others.
Unfortunately La Malinche herself apparently never wrote anything down, or at least nothing in her hand has survived the ages. And all the historians, scholars, and authors who wrote about the Conquest and La Malinche did so hundreds of years after the fact. The truth is, not one of these people knows the truth. There are no other documents available.
So, who do we go to for information on La Malinche?
The only legitimate method would seem to use all three of these sources, cancel out opposing descriptions of events, while considering those views that are in agreement to be factual. It is also important to read between the lines especially in the case of Diaz. Some of the events simply could not have happened the way he describes them and this is borne out by events that occur later or unknown to him. He certainly wrote down what he believed but its doubtful he always knew the actual facts. The best example of this is when Montezuma is held hostage by the Spanish. Diaz constantly writes how content he was with this imprisonment, but later Montezuma conspires with one of Cortés’ enemies, Narvaez, to set himself free- so he couldn’t have been all that content!
Finally, it is vital to remember that except for the Aztecs, none of the Spanish (including Cortés and Diaz) knew what La Malinche actually said to the Aztecs. Cortés could have told her to tell Montezuma that he (Cortés) was not a god and both Cortés and Diaz would have recorded it that way. However La Malinche could have spoken the opposite in Nahuatl to Montezuma and none of the Spanish would have known!