I need help convincing my seller, to sell! But How short should a short sale be? Does it matter at this stage of game?

I have several properties in short sale mode, one seller will absolutely not accept less than a $$ amount she put in her head. Seller paid $405K, 4 years ago for a 4 Unit Multi Family, North End of Historic, Westerly, RI. She owes $375K, she has it listed at $350K, I got an offer for $310K and she refused saying something like "if she takes too much less, it will ruin the market conditions" - This property assesses at $378K, and in good condition, updated fire code compliant, makes money, and has a good rent history. SHe has to sell because of a drowning interest/variable rate.

How can I convince my seller to "TAKE THE MONEY" - any words of wisdom??

Thanks Sandy Bliven, RE/MAX South County

Any mortgage broker's or agents have the right answer for my seller?