Have you really investigated all studios around you that are closer? Things change, and since you moved her to the studio that's an hour away, another studio closer to you could have opened up, or an existing one could have changed its classes and focus. I would -- without getting your daughter at all involved yet, because it could upset her -- investigate other options that are closer.
I am entirely "pro-dance" as you put it. My daughter is 11 and has three ballet classes and one modern class each week, plus rehearsals for shows, and is in her dance school's performing group (classical ballet and modern, no competitive aspect at all, so very different from competitive dance). There will be more as she advances in ballet. But when I tally up the hours you are spending -- nine hours of class time, plus six hours of transportation time for those, plus unspecified hours (probably lots) of weekend rehearsals -- you are doing a minimum of 15 hours a week of classes/transportation time and probably more like 20 many weeks, right?
If you have other children, what are they getting that's anywhere near that much of an investment of their time and yours?
I'm not saying "everything has to be equal"! No, it does not, and some extracurriculars simply require more time than others, period. But have you ever talked to your other kid(s) and husband individually and privately about how they feel about all the hours you are away or on the road or at competitions? Again, I'm not saying drop it or cut it, but I am saying you might get the rest of the family to acknowledge how they really feel about it. Especially if you have younger kids they may be feeling that sister's dance "career" comes first before anything in which they're interested. If she's doing 20 hours some weeks-- that is the same as a half-time job.
It's wonderful that she maintains good grades amid all the travel and she sure uses her time wisely. Great skills. But the real question I would have for her studio director (again, without your child present): If she is doing nine hours of class at age 12, what can we expect when she is 14? 16? Will she be expected to be here five days a week by that point, at which time it simply may no longer be doable with schoolwork and the commute? What realistically will be her class load next year and the years after? If you fear burnout now, what about in a few years' time?
That may help decide things for your whole family.
It's normal for dancers by age 12 or 13 or so to have very heavy dance loads and some kids at our studio who also do tap and jazz as well as ballet and modern are there five days a week by the time they're teens, often six days most weeks with rehearsals for shows thrown in. And that's all without the pressure of competition. So long schedules are normal and we do have kids who have quite a commute just to get to the studio but who love it there. So I really do see your dilemma.
If this is your daughter's second home, and she lives for it, and does not do it "just because I've always done it," then you do want to encourage her. I know folks who have rearranged their family's whole lives around one kid's activity, and others who changed dance studios or sports teams because one kid's activity was eating every second of everyone's time. But only you can make that call.