Many wedding traditions are no longer set in stone, allowing the bride and groom to create the wedding that represents them and is thoughtful of all of their guests. The question of if and when the guests stand for the bride during the ceremony is another tradition that can be modified.
Traditionally when the bride and her father, or other chosen escort, begin their walk down the aisle the mother of the bride has the honor of leading the rest of the guests in standing for the bride. Some brides though opt to have everyone remain seated so everyone has a better view of her, but this can seem a bit odd and disrespectful. Another option that we recently experienced was the officiant announced for the guests to only rise after the bride had passed their row. This was a great way for those in the front to have a clear view of her and the bride was still honored by their standing as she passed.
I think it would be appropriate for the officiant to announce “With the exception of the mother of the bride, please remain seated until the bride has passed your row.” This allows the mother to enjoy a clear view of her daughter and enjoy the moment with her.