Definition of "unsparingly"

But when Boshy's ill-spelt, hopeful letters came, her heart charged her unsparingly, though her carefully school-dictated replies to him were destined to contain no hint of failure.

1907, Barbara Baynton, edited by Sally Krimmer and Alan Lawson, Human Toll (Portable Australian Authors: Barbara Baynton), St Lucia: University of Queensland Press, published 1980, page 205