I know some people are suggesting to try tampons, but I just wanted to let you know to be prepared that if your DD does try them, it may not work out.
My DD13 got her period at 10yo & it came every month following that first time. Well last summer (she was 12yo) she got it on our first full day at WDW. She always gets it for 8 days & we were on a 9 day trip at BCV!! Tampons were out of the question & every afternoon while we swam in SAB, she spent in the room...thank goodness she'd brought her laptop!!
We ended up extending our trip by an extra day just so she could have another day in SAB.
We check-in to BCV for a 10 day trip this Monday...thank goodness she got her period 4 days ago!!
Here's a little

in hopes that your DD won't have it during your trip.