pop up message button on user profile page

Hi,
i would like to say thank you for making this awesome plugin. i have created a button on user profile page.
<a href="<?php echo fep_query_url('newmessage', array('to' => get_the_author_meta( 'user_nicename') ) ); ?>" data-toggle="modal">Send Message</a>
Logged in user redirected a page for sending this message but i want that form will come up as a pop-up. i can show that model pop up with short code like this
<div class="modal-body"><?php echo do_shortcode("[front-end-pm]"); ?></div>
is there any way to pass “To” within short code? or any other way?

Thanks
Rashel