Display several random posts, but make sure a condition is met

I have a custom post type for a group of people (employees). At first, I needed to display 7 random employees. That was easy

<?php 
    $args = array(
        'post_type' => 'employees',
        'orderby' => 'rand',
        'posts_per_page' => 7,
    );
    $query = new WP_Query($args);
    while ( $query->have_posts() ) { $query->the_post();
        //do stuff
    <?php endif;
    } wp_reset_postdata(); 

?>

But now I've been asked to make sure at least one of the seven is always a woman. The man to woman ratio at the company is 4 to 1.

I've set a checkbox that I can test for:

<?php if( in_array( 'yes', get_field('is_female') ) ){
 // this is a female
}

I need help putting it all together. I assume I need to keep track if any of the posts are displayed are women. Once I get to the 7th position if a woman isn't listed, I need to keep iterating until I find one.

Any suggestions?