Over the weekend, Avril, 25, and 29-year-old Wilmer were spotted at Los Angeles club Wonderland getting cosy.
An onlooker is quoted by US gossip blogger Perez Hilton as saying: "She had her hand on his knee and they were whispering in each other's ear, laughing. They even closed the club, sneaking out just after 2am."
Avril filed for divorce at a Los Angeles court last month citing "irreconcilable differences".
She is asking for a ruling to block Deryck - whom she was married to for three years - from receiving spousal support.