I think some of the contrast is because her pancreas is likely sputtering. If you get good numbers she can run with it, if you don't hit good numbers, her pancreas can't handle it. So that one drop of insulin might not in itself be making all of the contrast in the numbers, it may be more that it gives her just enough boost that her pancreas can try to take over. Just speculation.

We do see a lot though of this sort of "all or nothing" effect, where the numbers are either green or yellow, and it's hard to target something like a 120 nadir and actually get that.
I think it also means that you don't have to fear the slightly higher doses. If 0.5 left her high and 0.6 gave her good numbers, she could probably tolerate 0.7 or a little more just fine. It's not like she's going to hypo because you gave 1 drop more insulin, when 1 drop less left her running high. I think with her ketone history, if you are agonizing over tiny increments, you should generally go with the higher dose rather than the lower one. We tend to be a little conservative around here and lean towards the slightly lower dose when there is a choice, but I think in a lot of cases the slightly higher dose is the better pick. We rarely see low numbers here, or even the ideal ones, but we do often see higher numbers, and slightly higher cycles like this last one.
Not picking on you

just trying to counter my natural tendencies to undershoot, and hoping it will be a good reminder to others as well.