I would think that with all of her money and fame, someone like Britney Spears could get out of the task of being a bridesmaid. She was in a wedding over the weekend, and this celebrity gossip site has pictures of the dress she had to wear:
She and the other bridesmaid are attractive women with nice figures, and they look terrible in these dresses. The pale blue is a really unflattering color for both women, and the skinny belt with the angular halter neck look really severe.
Pale dresses like this one always hit my eye wrong next to a black tux.
I'm fairly certain that this is one of those times when the bride intentionally chose a difficult-to-wear gown style to make the bridesmaids look less-pretty than her. It's so bad.
Sorry Britney - one day I'll have something nice to say about your wedding attire.