Children have their own ideas about what they like, so when it comes to her birthday gift of a piece of children's jewelery, ask her what she would like. It's likely she will ask for a bracelet or some children's earrings. Children's bracelets come in many and varied forms, so ask her whether she prefers gold or silver. If she likes sterling silver, ask her if she likes children's charm bracelets, the type with clip on charms, or a European style charm bracelet. Perhaps a sparkly bracelet with cz appeals to her. Perhaps a pearl bracelet? Or whether she likes children's ID bracelets. If she wants an ID bracelet, you can have the nameplate engraved with her name or some loving words. She will be so thrilled with this personalised type of gift and she will love that you asked her opinion and allowed her to choose.
The same goes for earrings. There are so many styles of children's earrings. Mostly stud style, some have push on backs and some have safety screw backs, which are very useful for first time earrings wearers. Hook style is probably more suitable for older girls and teens, at which time, they may prefer a dangly style. She will be thrilled to pick out a style from the hundreds available online.