I graduated an idol and hired her as staff (she appeared as a stylist).  She still shows up in the Formation screen.  Is this a bug, or a feature?  It does kinda make sense that you could pull her in as she's in the building after all.  This was even the plot of an iDOLM@STER episode.

From the patch notes:
"The "idols" section now features a tab for graduated idols (in addition to the default tab, which shows active idols). Here, you can get a glimpse of how idols' lives have turned out after graduating."

The idol does not show on this tab.

Outright fired another idol, and she too remains in the formation screen...  So, at least partially a bug.  She does show in the "graduated" tab.

Hey, just pushed an update that should fix the formation bug.

If you hire a girl as a staffer she won't appear in the graduated tab, but that got me thinking that maybe I should just add her with a description like "Works as a dance instructor at [groupname]", I'll do that for the next update

Cool, thanks!