Counsel her. Put the facts of today's incident. You don't need to know which articles, let the Commander (who will ask JAG) figure that out. Tell her it's unacceptable to leave work (or not show up to work) without authorization.
Plan of action:
-inform you (or appropriate person if you're gone) of when appointments are scheduled
-inform you when she's leaving for appointments
-unexcused absences will be considered as dereliction of duty and dealt with in accordance with the UCMJ
Corrective training could be
-doing whatever you were working on by herself
-essay on importance of scheduling
-essay on what happens when Soldiers don't keep superior informed of what's going on
or plenty of other ideas..
Be Proud of what you do- and do it Well! ~me