Good idea! I assumed she meant Red but as you said – Red and Granny are in the Enchanted Forest. Sherwood is different, and Snow was gender neutral – she learned from “someone” in another forest. I’m on board with Snow learning from Robin Hood. Red taught her to track, but from what we saw of her in the two Red centric episodes, she wasn’t much chop with general banditry.
Also, I totally thought that was Robin Hood saving Regina from the executioner’s block until about halfway through the action. Is keeping the costumes very similar a clue?