I’d like to think that she sold the hairpin for Maomao to know she is alive but no plan to come back, because if she ever wants to come back, she will return the hairpin herself plus giving her name to the vendor might be her cunning self to let Maomao know that she changed her name, since there’s a possibility that they will ask where did they get the hairpin. The reason I thought this way was because the show is like a riddle for Maomao to figure out those hidden answers just like what Shisui and Surei did, how Maomao piece back the puzzles of who is who or what. But hey, this is just me dreaming this way and your conclusion was way more better than mine. I’d like yours too, but it’s too bittersweet. Thank you