Rinoa is a target in the Adel boss fight in Final Fantasy VIII, fought at the start of disc 4. In this battle, Rinoa is junctioned to Adel. If Rinoa is killed, it is Game Over. The start of disc 4 is the point of no return, as after Rinoa is taken to Adel, the party refuses to exit the Lunatic Pandora without saving her.
The player should cast Regen on Rinoa at the start of the battle, followed by Shell. The player can draw Regen from Rinoa for this purpose. Adel will frequently drain HP from Rinoa, so the player should ensure one of the fighters has the Recover command to top her up occasionally.