"in the most beautiful hand"
Graphology, the pseudoscientific study of handwriting as a means of adducing a person's character, has been around since the 16th
century but became particularly popular during the Victorian era. A self-consciously beautiful style — and it becomes apparent from the governess's narrative that her approach to writing is nothing if not self-conscious — did not necessarily betoken favourable attributes. Rather, it indicated egotism, jealousy and a manipulative personality.
Readers interested in finding out what their own handwriting is supposed to reveal might like to try this online test.