Myrtle if you can get it and lemon verbena would be good choices, if you're meaning stand alone pots of herbs which I think you are, lemon thyme would be good as well and lemon balm, calendula and marjoram would also be good to use on the table. If it was me though I'd go for alternate pots of lavender, lemon balm and lemon verbena, wonderful summer fragrances, all are tactile herbs as well, so guests can squeeze or brush the leaves to release wonderful aromas.
In the language of flowers Lavender is a symbol of devotion, Lemon Balm 'brings love' and Lemon Verbena attracts the opposite sex
Calendula symbolises joy, Marjoram symbolises joy and happiness whilst Myrtle is a classic symbol of love and the age old emblem of marriage. Ohh just had another thought, pots of jasmine would be nice and ivy interspersed with roses, all of them count as herbs and the jasmine and roses would add a wonderful fragrant touch. Hope that helps, do let us know what your daughter decides to use, such a wonderful idea to use herbs as wedding decorations.