Perhaps sounds crazy to you but have you looked into martial arts? Boxing f.e. doesn't involve much loading for the knees and is a very, very technical sport that suits former gymnasts.
Why would you have to "transition to another sport"? A sport is always worth doing even if you never make it to nationals or even get to be a professional athlete one day. It is about having a productive youth, getting movement skills for life, build friendships for life and get to know yourself...
I'd say she is very normal 5 year old kid, high energy, loves to move. Let her be, try again next year. Continue the privates. Nothing will be lost if she gets time to mature.
Do it way more slowly. Jogging, not running. If you can no longer talk in full sentences it is too fast. May be slower than walking in the beginning. Build it up from there. Jogging - walking - jogging and so on is enough. Three times a week, about 30-40 minutes each should be fine for an active...
No. Not if you do not abuse steroids. Stay away from Kreatin too. The rest will sort itself out (body type, nutrition). Olympic weightlifting never causes "bulk", it is not power lifting let alone Bodybuilding. Completely different sports. Anyways as an adult gymnasts you will need all the...
As a coach: If seven minutes of running are a problem your endurance is a problem. I would recommend going for brisk walks every day to get better at cardio stuff. If not for your sport (it will improve your recovery and thus make it possible to train more without getting overtrained or even...
Interval work and just aerobic work in general. You could just go ride your bike to school/work every day. That covers at least the basics. Add some HIIT at home (no need for impact work, do Kettlebell work, squats, deadlifts etc. instead) and you are all set.
Fries (fried in fat!) and hamburgers let alone chicken nuggets (fried in fat!) not cooked by yourself are usually highly processed foods, so yes, this is "fast food" to my German mind. Here this is nothing we would feed kids (!) several (!) times a week. These are treats for special occasions...
Fast food several times a week? Wow. Perhaps a cultural thing. In Germany this is not the norm and considered a treat for kids, definitely nothing to eat several times a week even for non athletes.
Please be very careful with Crossfit. It has a huge injury potential and is not ideal from a GPP perspective. I would stick to your gymnastics conditioning or add some olympic weightlifting (not for endurance like in many CF-Wods, just for strength and speed). Make sure you get a coach who knows...
It will be fine. You can not "overtrain" working out two times a week several days apart. Keep going, suck it up. If the pain is really bad try to add in light (!) strength work on your off days and use everything that increases blood flow, like going for a bike ride, light jogging, walks, hot...
She should be doing lots of little games and activites with other kids her age to improve strength and speed, jumping and having fun. Think tag or running up and rolling down hills and the like. That is more than enough for age 7. Weights are not advisable for any 7 year old ever. Distance...