Christiane Stahl says the reports, which have appeared in several European publications, are "the very incarnation of jealousy."
Stahl told Monaco-Info Wednesday that "only jealousy could push people to start such violent, such ugly rumors just a few days before a marriage."
Albert and Wittstock, a 33-year-old ex-Olympic swimmer, will be married in two-day-long festivities Friday and Saturday.
Stahl said the couple were "affected" by the rumors but added they are concentrating on last-minute preparations.