Lily felt conflicted; she often wished Severus smiled more, but at the same time, she enjoyed how his smiles were often reserved for just her. That made her feel beyond special.
Lily had no intentions of letting him go just because of what Harry had said. After all, this party was quite wonky. They could be seeing all kinds of people from alternate universes - and that's the only way she could see herself ending up with James Potter for a husband. Perhaps he was not an obnoxious arse in an alternate universe. That was certainly difficult to imagine, though.
She was touched at his words, feeling the sincerity behind them. It made her whole countenance light up, and she could not stop herself from hugging him. Severus Snape did not come off as huggable to most people, but he definitely did to Lily. "I would do the same for you," she promised him, meaning it.