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As howard said, where did that Picasa display on the left come from? Is if from the jpeg than is embedded in the raw file? Is it Picasa's conversion of the raw file? In either case, has any additional Picasa processing been applied (WB)?
Let's assume it's the jpeg with no additional processing. In that case, it's the result of the camera's auto white balance, contrast, sharpening, and color vibrance settings. The backgrond of this jpeg as a blue cast. Maybe that is "right", maybe not. We don't know the true color of that background. But that white balance makes the skin tones less yellow.
You clicked on the "white" background in ACR to set white balance, and made it neutral. No blue cast. As a result, the skin tones are warmer, more yellow. Maybe that is right, maybe not. If you don't like it, just lower the temperature until you do like it. Right or wrong, it's what you like that counts.
As for the exposure on the dress, ACR is applying some camera profile. If you have not changed that setting, you are probably getting "Adobe Standard". Try some of the other profiles to see what happens.
The Adobe profiles each have a tone curve built in. Some will darken shadows and brighten highlights more than others. They vary by camera model. On my Canon 5D2, the "Camera Faithful" profile has a softer tone curve than Adobe Standard, but that may not be the case with your 7D.
ACR will definitely give better results from RAW images than what in-camera jpegs produce, but there is a learning curve. The advantage of ACR becomes greater when the image capture is less than perfect. ACR can correct white balance and exposure errors much better than any program (Picasa, Photoshop) can do when working on a jpeg that has those errors "baked in."
With white balance, it's a major challenge finding a "true" neutral area to use. Many things that look neutral to the human eye are not really neutral. White walls or clothing are rarely true white. In fact, they are usually a bit blue.