For Flora you need to advance Mirel's event far enough until you had the events where Flora tries to help her with earth magic. Afterwards talk with the headmaid in your hidden bedroom and select Flora from her special screen.

For the bonus scene you need to talk with the guard at the bottom level of your secret prison. He'll give you a quest to get tentacle spores, which you can obtain at the hard floor of the Spire of Courage. The hard floor is unlocked during the events with Naevy. The spores are in the top right of the map where you fight the demoness. Once that quest is done a new dialog with Lace will trigger the scene.