If you have a copy of "Last Flight" written by Earhart, on Page 33, it gives an indication that she could well be using lean of peak and if she did use lean of peak she would not be able to lean any more now would she ? The only way after that to use "less" gas would be to retard (ease) the throttles slightly.
Except that if she tried that in a headwind she would in fact use more fuel. If she were to "ease the throttles" ie reduce power and therefore fly slower she would increase fuel consumption per Nautical mile (ie an adverse specific ground range). Between Emelia, Noonan and the various advisers along the way, they should have understood this and actually increased power slightly in a headwind in order to decrease fuel consumption/nm.