Late to the thread and was looking for a good post to reply to, but "when did she become MVP?". Different times for her various roles.
Obviously preventing the takeover of the Basilik terminus was an MVP moment. For Grayson, she's the MVP from Hono of the Queen through Flag in Exile. But the turning point for me -- which others have identified -- is her stint on the Weapons Development Board post Honor Among Enemies, and jerking up Hamish short for dismissing the recommendations made which arguably enabled the Star Kingdom to not only survive but become the pre-eminent space navy in the entire series.
My favorite other MVP characters, by the way, are Scotty Tremaine and Horace Harkness. Between the two they not only saved Honor's proverbial backside a number of times, but are some of her most successful proteges.