Please go to www.cpsc.gov and search "lead children's jewelry."
It's frightening but true: A LOT of children's jewelry contains lead at levels much higher than is safe. Kids can swallow it and get very ill. This is why, when she was small, my daughter never got any little necklaces etc. from the dime store or dollar store or anything like that. Not worth the risk There are recalls and alerts all the time about jewelry marketed to kids but found to have dangerous levels of lead.
As for real jewelry -- you mention a sterling chain and a pendant -- two is just too young. She is likely to forget she is wearing it when she gets busy playing, and it could catch on playground equipment or even something at home and pull on her neck. Sure, a thin chain might break, but before it does she's going to get hurt and will be terrified. Or she'll lose it and be upset that it's gone. When she is old enough she won't put things in her mouth EVER (and two is not old enough to guarantee that, I think), then get her non-toxic beads and let her make her own necklaces and bracelets galore.