It is still at the discretion of the Youth staff onboard at the time of the cruise. The closer a child is to the aging-up birthday, the better the likelihood of being allowed to move up early -- but it does depend on the number of children of proper age on that particular cruise. If the space is full, they will not allow anyone to age-up. Summer cruises do get full with kids on summer vacation, so it's hard to say; no one online here can give you a definite answer. I'd prepare her for "no" and then be happy if she's allow at Vibe. Enjoy your cruise!