LL,
Every child is different. My son's birthday is at the end of November and he began kindergarten at age 4. However, he had all the basic tools for school and then some. Academically he exceeded the requirements - could read, write, and do basic math. But, more importantly, he could share, pay attention to the teacher, follow directions, be polite, engage in group and solitary activities, play nice, etc. At the end of kindergarten, we debated holding him back because he is smaller. He is in first grade now and, other than his size, you would never know that he was so much younger. THe best part is, he really likes school. So, I think we made the right decision. My nephew is one year and one day apart from my son and they are holding him back. He is not ready for school. He likes to play in his own imaginary world, be boisterous, and emotionally he is very child-like. Both of our boys went to preschool, but their personalities could not be more different.
My recommendation would be to contact your school district. Tell them your situation. They may offer a skills assessment. Or maybe you can request a visit to a kindergarten classroom with your daughter to see how she feels about it. It is a really tough decision. We agonized over it.
Good Luck,
C.