function add_product_name_field( $meta_fields ) {

    $meta_fields['product_name'] = array( 'label' => 'Last Product Purchased', 'group' => 'woocommerce' );

    return $meta_fields;

}

add_filter( 'wpf_meta_fields', 'add_product_name_field' );

function get_product_data( $order_data, $order ) {

    foreach ( $order->get_items() as $item ) {

        $product_id = $item->get_product_id();

        $order_data['product_name'] = get_the_title( $product_id );

    }

    return $order_data;

}

add_filter( 'wpf_woocommerce_customer_data', 'get_product_data', 10, 2 );