Yesterday I was playing a game as Zarya. There was an Ana on our team, and though I was consistently the last one left alive in team fights (because Zarya never dies), I never saw the Ana use her ult. We ended up losing the game, at which point I inquired in chat as to whether or not the Ana ult had ever been used (strongly implying it should have been used on me). The Ana player responded that they did use their ult, but on the DVa, right before she exploded.
This made me wonder, if a big DVa is 'powered up', and her mech is killed, does the little DVa retain the power for the remaining time, or is it lost? And similarly, if a little DVa is nano-boosted and then calls in her mech, does she lose that boost?