I think it may be bordering on selfish vanity, turning this wedding day into being about you. It depends on how good a friend she is, but if its enough then you should feel capable of either grinning and bearing it, or telling her that you won�t go.
Plenty of time to try and overcome whatever angst you have about weddings, but if you are already getting sweaty about it and centring the day around your feelings, then it might just be as well to tell her you �don�t do wedding�s' and see how she takes it.