worked perfectly, thank you thank you!

The following works, but only when I update the parent theme vs child .. do I need to add all files under directory includes > wp_booster to make this change appear in my child theme?
function get_excerpt($cut_at = '') {

//If the user supplied the excerpt in the post excerpt custom field, we just return that
//HIS - if manual excerpt, trim to be 55 words vs entire excerpt
if ($this->post->post_excerpt != '') {
$custom_excerpt = $this->post->post_excerpt;
return wp_trim_words( $custom_excerpt, 55, '....');
}