she's a beautiful pony! i have her myself, however mines MIB.
i took a look at recent sold listings on ebay- the last MIB listing sold for 40 (the same price i got my MIB one at almost a year ago!) while the last loose one sold for what looks like just little under 30 bucks & had some scratches/stains on her paint. i would say 30 is a very fair estimate for yours- since it seems she has a few spots on her face?