In Western culture the bride has bridesmaids to look after her on the day of the wedding. For example, to help the bride with her train (the long skirt of the bride's dress), adjust her veil, give her tissues if she cries, helps her carry her bouquet, etc. The bridesmaids are normally the close friend of the bride or sisters of the bride. I guess it's to make the bride feel like she's a queen and she has people looking after her on her big day. Usually the best friend is the maid of honour, which is a special title to one of the bridesmaids.