I, personally, would start again with eggs you know are freshly laid and therefore will definitely develop at the same stage/rate/stages. I know it's hard to throw out eggs you know are viable but if they are at different ages, they are going to suffer one way or another at a later point and you will do nothing but fret and worry. She seems like she is firmly setting so should accept the swap.
My method for the move when I faced a similar situation was this....
I carefully selected freshly laid eggs and marked them with a pencil. I placed the new eggs on top of a fresh bedding nest (chopped straw) in a low sided cardboard box (A3 printer paper box lid!). I then went out after dark with a head torch, lifted the broody off her nest, took away her mixed eggs and replaced her on the already prepared new nest, in the same spot. This meant she would then just settle back down in the dark, as they do, but she would be in a movable box....hen, eggs, nest and all! It sounds like you may already have this set up in place???
I then gave her a couple of days to really settle back in, removing any eggs laid by other hens in the interim. Once I was convinced she was serious about the hatch, I went out, after dark again, and moved the whole hen/egg/nest/box ensemble in one 'piece' into a previously prepared separate house and run, where I could then leave her totally in peace to get on with her business without the interference from me or the other hens.
As far as number goes...I gave her enough eggs that she could comfortably cover the lot with her actual body (not just her voluminous feathers....she was a very fluffy Cochin) In her case, that was 12. She went on to successfully hatch and raise them all and I had a lot less stress as I was happy knowing she had the privacy and security offered by the new set up and that all of her eggs would hatch together. Incidentally, the new house and run were still in full view of the rest of the hens so she could hear all the familiar goings on and not fret about where her flock had gone!
Good luck, whatever your choice xxx