Beatrice and Eugenie haven't been mentioned in the Epstein files except in the context of their mother's emails to Epstein. I think it's fairly clear they weren't involved with the whole mess. It doesn't make sense to punish them for their parents' horrible actions. I think they are deliberately lying low and their not attending Ascot is a part of that. I think they must have discussed it with William and made the decision not to attend.