Barbara Collingwood was the second daughter of W. G. Collingwood. She married Oscar Gnosspelius in 1925.
Arthur proposed to Barbara twice (first in 1905), though she "took two years or so to make up her mind not to marry him". He also proposed to her sister Dora (LAR p44)(TLE p48,124).
He wrote in his autobiography that in 1904 Barbara "had not made up her mind to say yes or no (though) both her father and her mother would have been pleased if she had decided to marry me, (and then he) took No for an answer." By 1908 his relations with the Collingwoods "were the same as ever" despite their recognition that they would not marry. When he returned from Paris in the spring of 1908 and was "no longer hoping sooner or later to marry Barbara Collingwood" he started writing love letters to real or imagined people, some of which "to my shame" he posted (AAR p 127).
Arthur's 1916 book Old Peter's Russian Tales was dedicated to Miss Barbara Collingwood.