This is Meadowlark, and important supporting character in the fan fiction Project Sunflower, by Hoopy McGee. She is described as a “bright yellow unicorn mare with a light grey mane pulled back in a no-nonsense bun” (this was the closest-matching mane I could find to use). Light green eyes. Cutie mark: Open ledger (book)
 
I know how Derpibooru feels about Pony Creator ponies, especially original characters made using it. And considering the reception that the author-realized depiction of Meadowlark’s daughter Marigold got when I uploaded it two years ago, I wouldn’t be surprised if this gets a cold response, also. Anyway, I created this depiction of Hoopy’s character Meadowlark. For all the flack the Pony Creator (this was made with version 3) gets, it’s still an incredibly useful tool for sketching out rough ideas of what a pony character looks like for those with no ability to draw a pony well enough.
 
I’d add a tag for this character, but “Meadowlark, “oc:Meadowlark, and “oc:Meadow Lark are already taken by other identically-named characters.