Awesome that your daughter is interested in weightlifting! I press ganged my younger brother (13) into it this year and he's loving it too.
A few things from my experience of dealing with juniors.
1. Keep things fun and varied, focus a lot on technique and speed, strength can be built later.
2. Don't specialise early. Make sure you include all of the basics push, pull, squat, deadlift and mid section exercises and don;t just focus on the O lifts. We get our juniors to do a lot of core work (plank holds, sit ups, back extensions etc) as well as general "bodybuilding" type work (pullups, pushups, bench press etc)
3. Max 3 sessions a week of weightlifting, max 3 weeks of increasing load before a week long back off.
4. Progress slowly and watch for signs of discomfort or pain. Anytime a kid starts to rub a shoulder or screws up their face doing an exercise it's time to ask questions. at 8 you've got 20 years to develop a junior into a world class athlete but if they do an injury now they may carry it all the way through. At the first sign of pain (not muscular soreness) back right off for at least 3 days and re evaluate.
5. Physio screening - sometimes worth getting a physiotherapist or sports science / biomechanist to assess kids on a yearly basis to pick up any functional deficits that could lead to injuries.
6. Enforce good warm up, hydration and stretching habits. Our juniors are shocking at this and need to be watched constantly to make sure they warm up and stretch.
I think thats the main stuff, i'll have to get around to writing an article on this some day