Others have posted about this and said a diamond will be passed unharmed but the gold stud will look chewed up from the time spent in the gizzard. I wouldn't worry about the bird though.
Thank you so much for sharing your experance! this serves as a nice reminder for me to be more careful (mine just started shoulder sitting). Ive got 4 pericings and chickens who love to eat my hair.
I would think they nibbled on it and then tossed it and scratched it under a dirt pile never to be seen again. It should be lost somewhere on the ground. I have 80ish chickens and all are so picky, anything hard or odd shaped gets tossed and forgotten.
If you are worried about her, just monitor her for the next few days.