In 1936 Angela, Lady Brocket was photographed at Covent Garden with her friend, Lady Mary Manningham Buller (later Lady Dilhorne).
I think that Lady Mary Manningham Buller was wearing the same tiara which Angela, Lady Brocket was photographed wearing in 1935.
I don't know which lady owned the tiara, as I couldn't find any images of either wearing it again. My suspicion would be that it belonged to Angela, Lady Brocket. Her husband was very wealthy, and it is highly likely that she would have had 2 tiaras; whereas, Lady Mary's husband was not as well to do. But I don't have any concrete evidence.