Credit: Sam Sharma/Bruja, PacificCoastNews

Here comes the bridesmaid, all dressed in . . . green!

Pregnant Jessica Simpson was a bridesmaid at the Saturday wedding of Lauren Zelman (a friend and former assistant) and actor Bret Harrison at the Parker Hotel in Palm Springs, Calif.

For the rehearsal dinner the night before, the 31-year-old first-time mom-to-be dressed up her famous bump in a floor-length, emerald-green mumu with black embroidering; with fiance Eric Johnson supporting her, the Fashion Star mentor tottered in platform sandals.

For the wedding itself, Simpson walked down the aisle in a pink dress, with a wedding coordinator linking arms with her to make sure she didn't fall.

"She was a good sport about being a bridesmaid even though she is so pregnant," a source told Us of the bash, also attended by sister Ashlee Simpson, her son Bronx, actor Adam Brody and The OC creator Josh Schwartz. "It definitely wasn't easy for her to get around and help the bride."