I would also get an evaluation - you might be able to get one for free from EI. Most likely they will recommend some form of physical therapy to help her muscles (not just leg muscles, but this can include core muscles and brain integration stuff too) work together the way they are supposed to. There might also be other issues at play like a skeletal issue that needs medical attention. Problems like this are SO MUCH easier to address and resolve when they are caught early.
Mom of 4: Boy (10), Girl (7), Boy (4), Girl (2)