It's possible she's affluent, although it would be uncommon for her to have achieved it herself at a young age, but certainly not impossible. Also could be wealthy family or significant other. She could have stolen them, purchased them on credit and can't actually afford them, maybe they aren't real diamonds.
I don't like assuming negative things, so I'll assume they're real diamonds obtained legally, that either she purchased or received as a gift. So is she rich? Can't know unless you talk to her.
So for me, the real question is this: is she wearing them well, and am I attracted to her? If so, might as well chat her up.
She is wearing a lot of diamond to show them off I'd assume she's a gold digger that just hook a rich guy
Wealthy woman may have nice jewels but if you notice they wear in moderation or events and not a lot at once.
many wealthy people like to look poor so as not to be targeted for their money , while people with less have to over compensate an show off , like your question where the girl was wearing a lot of diamonds to tell every one she is rich