Seifer's lips are hard against Quistis' and she thinks, as she often does, I was someone's big sister. She doesn't know where this thought comes from but it haunts her, and each time she looks at Squall something burns inside her and she feels betrayal; for it's something like cheating, though she and Seifer are really nothing serious.
But she thinks about Squall, cursing herself for yet another conflict of interest: her favorite student versus her most mysterious. And she closes her eyes as her fingers find Seifer's hair, his tongue on her neck, wishing only to silence her thoughts.