Sidebar Fall to the Bottom on Mobile Phones

I’ve been using the Fashionista theme for a few days and while the theme looks relatively fine on my iPad, on my iPhone 6 the sidebar falls to the bottom under the content. My friend who has a Galaxy Note S3 also sent me a screenshot showing the sidebar at the bottom under the content. Can anyone tell me how to get the mobile version of this theme displaying so that the sidebar is displayed properly and not at the bottom.

Here is a link to my site Brown Sista and a screenshot here and here showing the problem.

Thank you ??