Thanks everyone! Sorry to be late to respond. Because of the time zone differences, most of your comments come in while I am sleeping.
With the first “necklace”, I just snapped the bracelet onto the collar using the bracelet fastener. It worked a treat and the metals (antique gold) matched. No further action required.
With the second “necklace”, I slid the bracelet onto the collar using the circle of the bracelet fastener. The bracelet is silver, so it did not match as well. Because of that, the hanging silver t shaped piece of the bracelet fastener kind of offended me. I think it would have looked ok if the metals had matched, but because they didn’t it looked more obvious that it was a bracelet. Fortunately the stones of the bracelet are somewhat hollow at the back and the silver setting creates a rim around the stones at the back. So I was able to simply tuck the t section into the back of the last stone, where it was held by the rim. It was fairly secure, although I wouldn’t hit the dance floor in it. Another idea would be to use some blu tack to hold it in place.
I think Adina removed the fasteners from hers, for a more integrated look. But I was looking for a quick and easy fix!
I also tried, but didn’t photograph, a much finer gold bracelet with green stones on the same collar. I thought it looked good without any changes to the fastener. I think because the metals matched. So I think the same idea can work with a finer bracelet and without changing the fastener. Worth experimenting if you like necklaces!
I have worn brooches as necklaces and necklaces as bracelets. Also belts as necklaces. It never would have occurred to me to wear a bracelet as a necklace. It’s great to find new ways to wear your jewellery