I don't know who this is, but the photograph is signed "Sincerely Yours Blodwen [illegible].17". This does not look unlike the Blodwen who appears in the photograph of Arthur (son of W D Morris) and Blodwen. However, since W D Morris was born in 1886, Arthur cannot have been born until about 1906, and would thus hardly have been more than 11 in 1917. Presumably his Blodwen would have been of a similar age, so I don't think she can be the same one. Or perhaps the 17 that is written on the photograph is not the year.
Click here for a full-sized image, or here for the unretouched original scan.