[2] After leaving St Leonards School in 1910, Sinclair attended Madame Bergman Österberg's College of Physical Training in Dartford, England, where she was a classmate of fellow lacrosse coach Cara Gascoigne.
She then taught at an all-girls school in Yorkshire and in 1919 accepted a post at Chelsea Physical Training College.
[4] Women's lacrosse differs greatly from the men's version, and with emphasis on stick skills and proficiency.
Sinclair believed the game should be played with feminine refinement, stating: "Lacrosse, as girls play it, is an orderly pastime that has little in common with the men's tribal warfare version except the long-handled racket or crosse that gives the sport its name, Its true that the object in both the men's and women's lacrosse is to send a ball through a goal by means of the racket, but whereas men resort to brute strength the women depend solely on skill.
In 1978, the Bryn Mawr School renamed their athletic fields in honor of Sinclair[1] shortly before her death in 1981.