If you happen to have web-based exchange activated is very simple because you should be able to access her calendar (Assuming you have the permissions).
I used to do that all the time but got tired of it so I wrote an program that we can all work/collaborate using a web-based shared calendar (like a gmail calendar but internal and custom made):
Anyway, try this:
See if you have access to your web based exchange server:
https://mail.mycompany.com/exchange/
If you do then try this:
https://mail.mycompany.com/exchange/mysecretary/calendar/
good luck.