In my view, that's OK. It's all part of the master plan. In classical music lessons, kids are always working on a show piece that they will play at the next recital. But they are also working on etudes, technique, reading, and so forth. They're likely playing in an enselble as well. And the show pieces are chosen by the teacher for having particular technical challenges that the student needs to work on. The kids who are brilliant at show pieces sometimes take longer to get their reading chops up to speed, but they do catch up. If you're playing show pieces at age 12, it means you've still got a whole decade to turn yourself into a complete musician.I will also suggest just gently, that in this day and age practicing a song over and over till you can put the best of 10-20 takes is somethibg that can and does happen and is a skill itself. A *different* skill to traditionally practicing so you can play on stage 10-20 *different* songs with an ensemble. An Instagram musician has a different skill set to a hired gun. Be aware of that when you see the best take from several hours of filming.
Basically the opposite of Jack of all trades/master of none. If this kid is giving clinics they are likely legit, but I imagine you would find while she is great at rock, she probably has been mainly focussed on that genre to get to her level so early.
I think the only thing that's unusual is seeing it happen outside of the classical realm. I didn't even start playing electric bass until I was a teenager, and it was widely considered to be an instrument that didn't need formal instruction. There were both bad and good things about that. I don't think every instrument needs the competitive atmosphere of some classical instruments. If you weren't lucky enough to start playing music at age 8, you still deserve a chance to play music.