Research to measure the effect of smoking on MS has found smoke exposure is associated with a higher risk of MS. The risk appears to be higher for women than for men. Because the study cites "smoke exposure" rather than "smoking," that means second-hand smoke counts here.
Of course, the conclusion is that more research is needed. Surprise, surprise! They said the preliminary findings needed to be confirmed. But they also said further study in this area might shed light on why MS strikes so many more women than men. That might be worth pursuing.