Now I worry with such a long break/different teacher she will end up hating school. She had another 14 weeks to learn and mature.
I am a primary school teacher.
I promise you, that unless there is an issue, they will be fine.
The schools KNOW this is a problem, so for reception arriving in year 1, they will ease them in gently, ge them back into school routine and go form there.
The other point is that she is going to mature and change over the next 5 months. Her own delevlopment doesn't stand still.
reception is a year of play etc. Well, what are they doing at home? They are playing? Be a bit more pro-active with their play if you can (and absolutley no guilt if you can't).
if your child is already reading, keep reading, they will keep learning and grow while off school as much as while at school.
Primary age kids, and also year 7 and 8, will not have any long term effects, and honestly, truly , honestly unless there is a problem, they will be fine.
Schools know this. They really do. They will be putting stuff in place to help everyone ease back in, they will not expect them to leap into the next year's curriculum.
They learn lost at primary, but a few months at home is a place to learn too. Different stuff maybe, but they don't stop learning.