Remove Username from 'Send To' user list?

When composing a message, is there any way to remove a user's username from the dropdown list that appears, and to just show their first and last name?

Right now it shows something like this when you fill in the 'Send To' field:
"Username - FirstName LastName"

I would like to only display:
"FirstName LastName" , so take out the username and dash altogether.

Any help would be much appreciated!

Note: I know you can change this by editing the plugin directly (through inbox-shortcode-controller.php's suggest_users function), but how would I go about doing this without having to directly edit the plugin?

Cheers.