Drew Barrymore and Cameron Diaz leaving Chanel in Beverly Hills on May 30, 2012. Credit: Patron/Broadimage

Drew Barrymore only has a few days left before she officially becomes Mrs. Will Kopelman.

The pregnant actress, 37, attended her final wedding dress fitting at the Chanel store in Beverly Hills Wednesday. She was joined by Cameron Diaz, 39, her best friend and costar in 2000's Charlie's Angels.

"Drew has been leaning on Cameron a lot," an insider tells Us Weekly. "Cameron has been very involved."

In fact, Diaz recently revealed that Kopelman, 34, gave her a heads-up before proposing in late 2011. "I knew Drew was getting married before she did!" the What to Expect When You're Expecting actress told InStyle UK.

While Barrymore and Diaz were in the Chanel store, Kopelman picked up his tuxedo and left with a garment bag. He was later photographed carrying a bag from luxe Parisian jewelry and watch designer Van Cleef & Arpels.

Earlier this month in NYC, Big Miracle star Barrymore tried on wedding veils in front of her future mother-in-law, Coco Kopleman, at an Upper East Side bridal shop. "He has this incredible family," Barrymore recently gushed of her future in-laws. "I am as in love with his family as I am with him."

Twice-divorced Barrymore is expected to tie the knot this weekend at her estate in Montecito, California. "Drew wants to get married before the baby comes, but doesn't want to be huge," a source once explained to Us.