WSD bikes are often the same geometry as non-WSD bikes. Trek WSD bikes are H3 geometry. But WSD bikes also often have different bits: narrower bars with perhaps shallower drop, shorter stem. Women typically have smaller hands than men and some brakes/brifters may have better size for women. I hated SRAM double tap because I had to really reach to shift from small to large front ring. Sometimes, you might also see shorter crank length. Whatever fits best is what she should get.
Your wife's bike purchase should be a "we" or "she" event, not a "you" thing.