If the chamois is too wide for you it will chafe-the stiffness of the chamois makes it want to be flat, rather than bent, if it's too wide it sort of "pops up" into the inner leg which then chaffes with every pedal stroke. The width down there has nothing to do with your overall size-so you might need a narrower chamois than most. I'd compare men's and women's, and try the narrower to see if that relieves the problem.