That's the answer I was afraid of. First, I understand the demand of being a competitive athlete as I'm a former college baseball player and competitive weightlifter. Second, I understand the benefits of a ketogenic diet for someone with T1D as I've implemented the approach myself when it was necessary.
My concern for your daughter lies around the fact that you mention looking for "Balance," yet your primary focus seems to be around her blood sugar levels. While that is a top priority, it isn't necessarily the ONLY priority.
There's a lot of evidence to suggest that a ketogenic diet is harmful to a child that's still developing. It's often great for a fully grown adult, but that's a different topic,
While ketogenic diets have been proven to be beneficial for athletes, those athletes primarily compete in endurance races where short bursts of energy aren't as necessary. Carbohydrates are absolutely necessary in those types of situations like a sprint or short swimming distance.
Growth spurts are "A *****" because her body is demanding nutrients to continue growing and developing. Consider that the ketogenic diet is hindering that growth process and even blood sugar levels may not be an enkei treat good thing in this case.
Bottom line: I hope this is something you've thoroughly discussed with professionals and it isn't just something you've read online. The dietary approach for an active child needs to be much different than that of a fully-developed adult. That's not to say that your daughter should eat whatever she wants (I've seen the negative effects of that as well), but in your own words, there should be a "Balance" rather than so many compromises.