35mm Conti’s on the FX rims might only measure 33mm or so installed ? (if they are like 35mm Terra Speed) - but 33 should be sufficient
Yes, the GP Urban was noticeably narrower than the stock Bontrager H2, but I am not sure that we have the same stock rim? Mine is a 2016 FX 2 (which was one level up from the very base level), whereas your wife older 7.5 FX would be roughly equivalent to a FX 5 in the same model year, so might have come with better rims? Despite being narrower, it is a much better tire than the stock one.