In Sempre Libera, Violetta sings "Libera" (free), "Gioia!" (joy), "Follie!" (folly), and "Piacere" (to pleasure). So it seems she has forgotten her anxiety of before. But then suddenly a voice drifts in from the outside... a voice Violetta knows. The voice of Alfredo, Violetta's only faithful admirer, drifts in. She - being the fallen woman that she is - scorned him for being faithful, laughing at him. But that didn't change Alfredo. It did change Violetta, though. The melody Alfredo sings in the distance recalls when he first revealed his faithfulness to her, and it haunts Violetta, but she nonetheless tries to regard it as "Follie!" and enjoy herself. The words describe love, but in a different way from the love Violetta knows - "Mysterious, high, both cross and pleasure..." Violetta does not know of anything like this, and is disturbed.
The sad song of before, Ah, Forse Lui (Ah, Perhaps He...), spoke not of death, or pain, or really anything like that... and yet, it terrified Violetta and brought out mourning from her. It spoke of Alfredo, oddly enough, and Violetta considered to herself whether to actually stop and have love, serious, true love. She has never even thought about this before - Violetta is a prostitute, you see, originally from very poor beginnings - and faithful love is a strange idea to her. And a terrifying idea. Violetta's carefree joy seems to come from her later thoughts, that she must be free and enjoy herself, and love and party as she pleases, and only anxiety comes from thinking about faithful love and giving things up. How familiar.
Poor, poor Violettas. A lot of them. They agree so much with Violetta in the beginning, but they ignore what happens later. Even she caves in, and finally gives herself up to the true love of Alfredo. But it is still about her for a while. She lives with him and loves, but then one day, something happens. Alfredo's father comes to Violetta, requesting a simple thing. He speaks of Alfredo's sister, unwed, weak. She will never wed or be cared for properly if Alfredo and Violetta's relationship does not stop, because her reputation will be tarnished by it. So Alfredo's father, Signor Germont, asks Violetta to end it, pleading with her for the sake of love. But Violetta refuses. It is her love! Alfredo is hers now - what business has anyone to end this joy? But then, thinking once more of the words about love Alfredo once sang to her long ago, Violetta finally agrees. Now she fully acts in love, though she knows it will be hard. Because she can see Alfredo, her love, in the weak, unknown girl so much in need of care. And so Violetta gives herself up.