I think that $12 is a pretty good price for a single G3 pony. If it were me, I would offer her for sale here, especially since you already have the picture posted- most of the work is done! Heck, if you just said in this post that you are looking to sell her, I think there are a couple people who would PM you about her. You could see if anyone wants her for $15, and if she doesn't go for that, then you can put her in a lot.
Your pony, though, just thought I'd toss my input into the thread! Good luck!