You are wrong. It appears that Melania does campaign for her husband.
http://www.thegatewaypundit.com/2015/10/the-wow-factor-melania-and-ivanka-trump-to-hit-campaign-trail-in-coming-weeks/
http://conservatives4palin.com/2016/01/melania-and-ivanka-campaign-for-donald-trump.html
She joins her husband on stage sometimes, she does not go out and campaign for him. She does not raise money, make speeches, appear on her own.
She stays home and raises their son.