Actually, I am a personal trainer and I lift all the time. German volume training for growth. I just put my head down, do my work, and stick to my rest times. In and out in 1.5 hours. I think I know what I'm talking about.

Additionally, I have talked with many ladies who went for too much too soon and we end up with eating disorders, all or nothing attitudes, and an inability to see when the workouts they are doing are actually detrimental to their health. 15 is a really impressionable age, and until OP finds something she actually enjoys doing for 2-3 hours at a time, pushing herself for that long initially runs a strong risk of being detrimental to both her physical and mental health.

Wellness incorporates way more than just physical fitness (not the same thing as physically healthy, btw). And quite frankly, with today's Instagram body culture, someone has to be out here reminding folks of what healthy habits actually are and advocating for wellness.