2mm doesn't seem like an extremely wide gap to be concerned over. How humid is it there in the summer? Do you think the floor needs that space to expand?
There's probably a solution - (some product that is more flexible than wood putty) that will allow the boards to expand. I would think that the gaps could be filled with polyurethane or some plastic finish.
Tell her you will be willing to fill in the gaps - but not until summer. Then you know how much of a gap you need (and maybe she'll forget about it by then.)