A moustache bar might interfere with mounting a Wald basket because of the forward projection of the bars, especially if you're using standard drop levers mounted at the front of the bends (which seems pretty typical, if you're running brakes.)

If she wants the angled-back hand position of moustache bars, check out Velo-Orange "Tourist" or "Milan" or Nitto "Left Bank" bars. If she wants more of a straight-back grip, Nitto "Promenade" or "Montmartre" bars would work, or V-O "Belleville" for a bar with no rise at all.