They should call her Yhsrettulf and her blind bag blurb should be "YHSRETTULF is Fluttershy's EVIL TWIN."
Possibly a tiny goatee, too?
OMG I SUPPORT THIS! SEND TO HASBRO!!!
for real
They should make her the only blind bag pony with show-accurate Fluttershy style hair, too . . .
Seriously though, put her in a three-pack with a little removable cap and mailbag and call her "Ponyville Postal Pony" or "Ponyville Express Pony".
The other two ponies in the assortment could be, I dunno, Braeburn and Applejack? I'm sure they exchange letters. And experience tells me they won't do a three-pack without a member of the Mane 6 in it.