You can try this code with a custom function connected to : woocommerce_email_recipient_new_order
add_filter('woocommerce_email_recipient_new_order', 'adding_vendor_email', 10, 2);
function adding_vendor_email( $recipient, $order ) {
$recipient .= ",vendor@yourdomain.com";
return $recipient;
}
, ...
function.php ( ), .
woocommerce_email_attachments... .