why is my above grade second grader losing her focus n struggling with math in second grade

Second to third grade is a huge jump in mathematics. Place value in second grade goes up to 1,000. In third grade they get into hundreds of thousands and hundreths as well, usually within the first two weeks! The pace only gets faster from there.
Your child may simply need time to get used to the pace, learn to copy problems out of a book or off the board or even the logistics of setting up the paper and planning the space needed. If she is truly above grade level, it shouldn't be long before she is back on track. Give her the gift of a little time, especially if the teacher is not alarmed at the types of mistakes she is making.

You really have to look close at exactly what she's struggling with -- or better yet, ask her. You'd be amazed at how kids can tell you exactly what's going on. It could be as simple as she's expected to write her numbers in smaller spaces and keep them lined up and that could be hard for her. Also, third-grade is a time when a lot of reading difficulties come to the surface (the saying is in third grade, they go from learning to read to reading to learn). Kids before 3rd can hide that they're having difficulty because the texts they are using are easy to memorize. So, your daughter could be having trouble reading the word problems. Or since math knowledge builds on itself, she could just be a little confused about one particular bit of math knowledge -- her multiplication tables, for example, or what different math terms mean -- that her teacher expects her to know and so has trouble with the next lesson. The quality of instruction, of course, could affect her ability to learn and her desire to focus. The classroom could be chaotic or the teacher could be intimidating so she doesn't feel she can ask a question.

sorry! i meant third grade