What you don't see is the daily training she goes through. I can tell you without even knowing her that she trains HARD daily and is meticulous with her diet. That is what it take to be a champion.
I bet she squats 2-3 days per week, at the very minimum. Nothing will ever replace the squat when it comes to overall leg development and size. It is truly the best exercise you can do.
Not a smith machine squat, not a hack squat, not a front squat, a real squat where the bar is resting on your traps.
Master the squat and focus on increasing the amount of weight you can squat and I PROMISE you will get the leg and glute development you want.
Cutesy exercises like glute kick backs have their place but the squat is the 'bread and butter' for developing and toning the glute muscles.