Hi,
Due to my job, I fly on four planes a week. It would be very kind of you to advise your friend her beautiful pendant is not permitted ensuring it isn't taken away on a future trip. TSA works very hard to ensure passenger safety and occassionally some small items are missed, but at some point, they tend to catch them. Several times, I've witnessed frequent flyers having to give up or throw away an item they've 'flown with in carry-on luggage' because a TSA agent was being diligent.