Has she? She may have given in on international trade and on Wall Street regulations, but when it comes to single-payer and other issues, she has (more or less) held her ground.
I don't get why singlepayer is so necessary for a Democratic nominee, or even being used as a measuring stick for how left you are (I see it used in this fashion quite a bit). For the time being, it will not pass Congress, even if we had a supermajority in the Senate and control of the House. Democrats will not risk losing control over healthcare reform
for the 3rd time. They will put their own interests ahead of that this time around, should it ever come to that.