$300 for “good” jewellery sounds like a relatively low price to me…if I was buying a gift for my wife (yeah I know, differents ages etc) that would be my starting point, I would be more expecting to pay in the $600-$800 range for even an average gift.
And yes, we don’t have all that much money.
As to whether or not the kid can handle the gift - well only you can judge how likely the item is to get lost.
Depends on the child, really. As others have said, I’d recommend keeping it in the “special occasions only” category. Unless, perhaps, it’s something like a gold chain that never comes off. Is the child in question reasonably responsible with her things? Can you afford the 140 bucks? Would you be heartbroken if she lost it 2 weeks later?
Our own jewelry-giving has been to a slightly older age range:13-15 year olds. our 3 oldest nieces each received a pearl necklace (bought some years earlier) for their confirmation / bat mitzvah. Our next niece received an opal pendant at about age 6-7, at the time her adoption was finalized (happened to be in October, which also happened to be her birth month, and opal is the birthstone). In that situation, we suggested to the parents that they maintain control over the necklace except when it was being worn. The older nieces presumably held onto their own necklaces, we haven’t asked. We recently bought an emerald pendant for a Hispanic girl celebrating her quinceanera.
My daughter is 12.5 and I wouldn’t buy her an expensive necklace such as you describe, but that’s because she wouldn’t take care of it. Heck, she begged for years to have her ears pierced, we let her do it at 11, and she has lost earrings every time she changes them herself. Though we do buy 14K gold ones (anything less made her ears get icky), they’re tiny and cheap enough that we don’t worry about losing 'em. Nowadays she’ll wear a single pair for months anyway. She simply doesn’t care.