Tried myself on this only spoken of scene were Franziska Von Karma spends all night to safe Maya Fey during Bridge To A Turnabout. We never really get the reasons why she is so desperate to get her out of the Sacred Cavern. 

In my shippy brain everything points to Ziska is rather fond of Maya, not sure if she’d stayed if she knew Maya was not the one trapped there

"...Exactly. She has been out there all night, trying to remove those trick locks. With the head nun's assistance, naturally."  ~Edgeworth