Starting point is what level of competition is she at. You start out local, graduate to regional, then national, then international. Sports have different ages at which peak performance is expected, and that dictates your progress. Gymnastics need to be in international competition by the time they are 16, bicycle racers by the time they are 20. This difference of four years makes a lot of difference in your lifestyle.
Training time varies a lot from different sports, but archery is not an endurance event, so it can end up towards the short end of time. I don't know archery, but my guess is the typical day would include about 1 - 2 hours of technique and sport specific practice. Then another couple of hours of strength and flexibility training. Then another hour or two of recovery work, such as whirlpool, massage, treating strains, and so on and so forth. At least one day a week would be long, with the idea being to get her used to shooting when she's exhausted. For two players who are evenly matched, he or she that lasts the longest will usually win.
If she's competitive at the regional level, her school is probably making adjustments to deal with her sport. Immediate adjustment is dropping the gym requirement. So she might be on a late arrival and early release program. I don't know how many calories an archer needs, so I'm not sure how school lunch would fit in. Calories at the Olympic level for a 21-year-old male varies from 2,000 to 8,000+ per day. Higher calorie sports can have a lot of issues with the size of a school lunch, as well as longer eating times.
At the regional level, she'll begin doing national competitions.
Once she obtains the national level, she'll be spending time at the Olympic center with the national coach. Normal school tends to become impossible, and tutors or home schooling is used. The Olympic committee frowns on not being educated, but the reality is it happens a lot.
One way to determine the age for national and international competition is to look at when juniors (if there is such a division) ends. Money and parent's ambition are big factors also.
Doctors who specialize in sports medicine have become very good at identifying the long-term consequences of injuries.
Jim Clark-Dawe