gistfile1.php

add_filter( 'wcdrip_custom_fields', 'drip_add_first_last_fields', 10, 5 );
function drip_add_first_last_fields( $filters, $email, $lifetime_value, $products, $order ) {
	unset( $filters['name'] );
	$filters['first_name'] = $order->billing_first_name;
	$filters['last_name'] = $order->billing_last_name;
	return $filters;
}