Value-wise, I'd guess b/w $5-10k. Prozini knows this market and is giving you good advice. Continuing her race career is certainly an option and as long as you don't have a problem running her in claiming races she could do well for you.
Blue Domino is correct - she doesn't have an overly commercial pedigree and as a BROODMARE prospect she wouldn't bring much. But, she's selling as a racehorse. Makes a ton of difference! A horse that just won by 4 IS a decent runner by most people's standards.
Whatever you decide - hope you can attend the sale and have some fun!