All tires and rims are designed to a standard set by ETRTO. Campagnolo (Fulcrum) design their products to shoot for the outer dimension of those tolerances. They do this to ensure the tightest fit which they feel is the safest.

The downside is that some combinations can be VERY difficult to mount, especially on the road and especially with new tires.

Michelin and Mavic have been partnering up over the last few years and coordinating their efforts (think UST) and so are a good combination (but in some cases are outside of ETRTO which means other combinations don't always work as well).

Tires will loosen up a tad with use and this can sometimes make a difference. I'd suggest putting a few hundred kms on the tires and then swapping them back onto your wife's Fulcrum wheels and see if the situation has improved any.

Good luck.