Unfortunately, this is a limitation in How CKEditor works when adding divs. it will treat the new div as a part of the existing div.
the only work around i have been able to find is to add a new block element to the page like a bulleted list, that would get added outside of the existing div, then with the bulleted list selected, add the div, this would add the new div around the bulleted list.
now in the tag selector, select the UL tag, and click the bulleted list button again to remove it, I have found this successfully creates the new div outside of the existing divs, the only draw back is that content inside the div is enclosed with a p tag that would need to be removed in source code.