According to the passage, the inference that can be made about Elizabeth Cady Stanton's personal qualities affecting the women's suffrage movement is that:
Her ability to write and speak helped get the movement's message heard by the public.
This is supported by the description of her as a "master of words" who could "write and speak to perfection" about the concerns and feelings that Susan B. Anthony, her collaborator, could not express herself. This capability helped articulate the movement's goals and ideas effectively to the public.