It definitely depends on the child - let her decide choice how much she keeps up. She may lose interest and find new priorities, or decide she does want to invest all her spare time.
My DS18 is now at a conservatoire studying contemporary dance, so obviously maintained around 20 hours of dance a week, even through A levels. He managed to get all his homework done through a mix of in his frees, and around his dance classes. He didn’t do any other activities though, and crammed a lot of his dance hours on weekends.
DD12 is following in his footsteps - does dance six days a week, as well as trampolining, school music ensembles (and lessons, but they’re in school time), and being part of school’s netball team. She’s only year 8 so time will tell how much she keeps up!
DD14 (year 9) is sporty but has not developed the same degree of commitment to one sport - she just on the school netball and football teams, and does hockey locally on Sundays for about 3 hours if there’s a fixture (just 90 minutes if not). She also volunteers at Brownies and does music ensembles. You may find DD loosens her commitment to one area and branches out to lots of hobbies and activities.
It’s manageable if she wants it to be - if it starts affecting her energy levels and school work, and she loses interest in anything, then encourage her to drop activities. I’ve had to force DD12 to give up activities before by making her choose (ie dance or gymnastics, trampolining or Brownies when she was younger).