Complex sentence: In 1913, one of her paintings was included in the seminal Armory Show in New York, which Quinn assisted in organising--he had sent John a telegram requesting "Four (or three) Gwen John"; her reply was "One Gwen John".
Split into simpler sentences: In 1913, one of her paintings was included in the seminal Armory Show in New York, which Quinn assisted in organising. Quinn had sent John a telegram requesting "Four (or three) Gwen John"; her reply was "One Gwen John".