Override Non-Standard Files in Child Theme
Unfortunately, with the way child themes work, they won’t recognize non-standard WP files (template hierarchy) in this example widgets.
What you can do is to copy those files/folders from the parent theme and into the child theme in the same structure then in the child theme functions.php use:
include (STYLESHEETPATH . '/admin/sidebars.php');
The STYLESHEETPATH constant will apply to your child theme instead of the parent.