Water is also a symbol of femininity . The lotus flower (also called water lily), blooming high above the muddy waters that give him birth, symbolizes overcoming any diffuculty, and the tiger lily is a symbol of prosperity.
The whole design is thus a wish for prosperity and joy, following a change that will take Beatrice to overcome every hardship she may encounter.
The lily bud just wants to emphasize this change: the flower that is going to bloom.