Kinda odd they went for bracelets when we know those signify engagements. With how defensive she is about the other girl getting close, I would think she'd realize how that looks and stop it rather than being part of getting everyone to wear them.
Like rings in our world, it may depend on the design, what it's made of, and where and how it's worn. From the other two, it looks like that specific meaning comes with a gold bracelet, not a woven one.
On a separate note, after handing over the diagram,
now Hiro wonders if he can trust him? The shopkeeper could've also just said nothing, feign ignorance, then spirited the idea away, registering the patent in his own name, and reaping all the profits and prestige for himself.