We have a lot of broodies - and from my personal experience, this is what happens - if the hen is broody, but not sitting on any eggs, I can sometimes get away with moving her, because once she sees some eggs, she is delighted, and it takes her mind of her new residence I think. If the eggs are already under the hen, thats a different matter - she has chosen to lay there, and if you move her, its likely she will pick herself up, and walk back to the place she picked. She may not, but thats what usually happens here.
I can see your problem - adding eggs to the ones already there, is probably not a good idea, if she has been sitting a few days - otherwise the "new" ones will be behind in hatching. Not a problem if she has just started sitting.
Suppose only way to find out is to carefully put eggs in new place, then move her, and see what happens.
Good luck!!