My son's Kindergarten teacher said my son didn't fit in, but she was the type of person that was very cliquesh ( if thats a word).  My son also struggled for the first half of first grade.  We then moved to because of my husbands transfer and my son enrolled in a wonderful school that believes that each child is different and special and they teach to the individual differences.  It is such a supportive envirnment that all the kids just flourish.  I too was like you, my son was so social as a preschooler, I just couldn't believe the things they were saying about my child and it broke my heart. 

Don't give up on your child she may not be in the right type of envirnment for her to succeed.