Actress Cameron Diaz has reportedly asked partner Benji Madden's sister-in-law Nicole Richie to help her plan her wedding.

Diaz, who sparked rumours of her engagement to Madden when she sported a new diamond ring at various events here, has turned to his stylist sister-in-law for advice, reports contactmusic.com.

"Cam (Diaz) has never been a big fan of weddings, so she has no idea where to start," OK! magazine quoted a source as saying. The 42-year-old actress has been scouting Napa Valley in northern California for the perfect venue.

The couple are expected to tie the knot next spring.