I agree with talking to her piano teacher. If the teacher is a member of your states Music Teacher's Association there are more opportunities. My DS6 has been playing for almost a year and is progressing rapidly. His teacher totally understands him (she's a very gifted musician and plays multiple instruments) and had him in his first competition this last winter (which he won his division

) and he will be doing a Piano Exam this weekend. I highly recommend the Piano Exam. He will be tested in a variety of areas in piano theory and has to play 3 pieces. It has been very hard! Your DD8 might enjoy the technical challenge! It's been amazing for my son who has not been challenged in school this year and he truly loves it! It's been very empowering for him.
Also, our state piano competition is based on age, not ability. This is why his teacher signed him up for the Piano Exam. There are no age restrictions so your daughter can compete at whatever level she is at. My son thinks this is very cool!
I also agree with a second instrument if she's interested. Or, get a keyboard and she can start a band with some friends! Does she like to perform? She could also try recording and writing her own music at home. My son loves to compose and we purchased an inexpensive recording device and he can now burn his own cd's. He's going to work on mixing in Garage Band this summer. Good luck!