Britney was an "honorary" bridesmaid at the wedding of her cousin, Laura Lynne Covington, Saturday afternoon in Amite, Louisiana, according to People.com.
"When her brother walked her down the aisle, she looked stunningly calm and beautiful," says one wedding guest. "She was very pretty, low-key. She was not the center of everything, just pretty and calm and collected."
The wedding was held at the First United Methodist Church, the same church where the funeral for Laura Lynne's mother Sandra was held in January 2007.
Britney reportedly hung out with sister and "fellow bridesmaid" Jamie Lynn, who carried along Maddie and "sat at a table off to the side and visited with local people she knew," says the guest.
"There was no fanfare," noted the guest. "With all the star power Britney and her family command, it was still the bride's day."