She loved him. She loved his mind. She loved his drive. She loved his inner strength. She loved him enough to not love him.
She treasured the memory of their one and only night together. She treasured every word, every touch, every kiss they had shared. One intense, emotional night when they had cut free of their restraints and loved each other wholly.
But she was realistic. Loving each other would cost them everything. Sometimes love wasn't enough. If they chose each other, they would lose the people who mattered most to them. They would destroy everything they had built here. Leonard would be devastated. If Leonard left, Howard and Raj would follow. If Howard left, Bernadette went, too. And Amy? It would crush her. Not even for each other could they do that to the people they loved.
So, they settled for friendship, and their memories. They loved each other dearly. But they loved their friends, too. And as Sheldon's hero said (and heaven help her if he found out she was paraphrasing) the needs of the many were what mattered.