I let my kids travel as they wish in math. It is much easier for a teacher to hand an advanced math whizz an extention book than to reconstruct the entire English corriculum for one kid.
They are not hugely ahead maybe a solid year and another year in some areas. They lack in some areas ( measurement, And they memory work of multiplication....they can skip count by whatever so never needed to memorize it). But they are all very confident with their answers.
in the early years (first 2) of school all kids will do basic math to ensure a solid understanding of concepts. If I was teaching I would probably do this too. If you miss one small thing it can really unbalance later learning. This is why I would advise go ahead with math but be sure to checkoff your countries syllabus to ensure you cover all areas.
I wish I had done more math with them not less
As to reading Lee, don't stop yet! Not just before she grasps it. Go to at least the point where she can read through Dr zuess (ten apples up on top is a good basis) regardless of how fluent it is if she can get those sight words set in her brain all will be well, and basically sound out the rest of them. They tend not to make kids read through every book in a series now, but it still happens
it is teachers choice often so fight hard if they try to make your daughter do that. Nag daily! All teachers will eventually cave to get a parent of their back
And definitely don't leave the writing behind, it will be the one thing that the teachers use against you!