Child Theme over write rules

Child themes only handle template files. The file widget.php is loaded by the functions.php of the parent then you need to do the same with you new file is the child theme.

And if you want to deregister the sidebars loaded by the parent, you can try that :

add_action("widgets_init", function () {

    remove_action("widgets_init", "himalayas_widgets_init");



}, 2);