Puberty at age 9?

My daughter turned 9 this past November. About 2 or so months ago she mentioned her breasts had lumps and was tender and sore. Obviously it was breast buds forming. And today she mentioned her lower left side was hurting. Do the ovaries do anything at that age? Since it's puberty? I gave her motrin and she sit with a heating pad for a while and she says it feels better. Muscle? Overies? I don't know. Thoughts on what it could be? I've read her period may come 2-3 years after the breast buds form. The breast buds formed 2 months ago or so. So would her period be already trying to come? Is the pain her overies? I have no idea.