Leia holding Padme’s necklace would have been good if Ben spoke with Anakin rather than Han. I imagine, in the world where Padmé went to live on Alderaan, it was still buried with her and/or destroyed along with Alderaan.
Or, if you want the time stream to correct itself around this distortion more thoroughly, she was taken back to Naboo for burial along with the necklace at some point.