Thinking of it this way, it is safe to speculate that Russia, and, consequently, the organization behind the setting up of the Widows, of the Black they had some knowledge, albeit moderate, over the Gems of the Infinite, bringing Natasha Romanoff to a better understanding of the mechanisms of the attainment of the Jewel of the Soul, perhaps, in a way, the film the end of the Avengers does not even have a clear.
One more thing: who is the “spokesman,” which explains how to get the Jewel of Life.
Of course, there are flaws in this theory: if the In I knew ahead of time that the sacrifice is necessary, or some way to get the gem by means of a suicide, even then it is not permissible, because it is not counted in the energy-used to you used to? It can be argued that the artifact came from the poem, ” because I felt that the pain of loss is real… it’s that the Red Skull would Natasha felt that she would be somehow to break that rule?”
Ok, so we might be exaggerating, but this is Marvel, after all. “Make sense,” it is not a requirement of the company, in the event it will need to explain the death, or the resurrection of a character beloved by the fans, and a sizable audience had asked the company to give her a way to “revive” the Black Widow, and then the audience it has.