I could better answer this is I knew the resons why the teacher thinks she is not ready. But I have a child of my own who I enrolled in kindergarden and I can see he is having some problems with the structure of learning, so I am homeschooling him next year, and a some years after is the plan.
I had my my first child at 40 and I think the expectations for little kids are crazy high.. if you want her to stay in class keep her in and time will tell, if it sresses your child out - wait and maybe she can join in after winter break???
you have options.. -- maybe preschool another 6 months would be Ok for her? maybe she needs more tha 3 weeks to meet her skills???... kids grow fast -- why push it? they will come to their own when they are ready...all kids learn differnt.. maye its the teacher and not your child.??? lots of questions that need some more searching...