Melinda Button was Dick Casablancas' wife briefly in season 3.
She and Dick went on a date and ended up in Las Vegas. Melinda left her little sister, Heather, with Logan Echolls during his depression after Veronica broke up with him. Logan got a call and Dick said he was married, now on his honeymoon. They divorced a few hours after the wedding.
Melinda's father ran out on both her and her little sister.