If you don't mind the expense, for a special occasion, why not get a good Strelitzia Regina ('Bird of Paradise flower) in flower (they flower at this time of the year) in a large pot.
If your daughter has somewhere to keep it frost free and light over winter, it will flower every year after that and has such a distinctive flower. They are also quite easy to look after.

You don't say when the wedding is which has an impact on our suggestions

Yes, do you want flowers or structure? A large topiary specimen would look good. You can hire potted specimen plants, apparently. Google 'plants for hire' and choose UK websites only.