It needed to be done. She needed to let him know that when she had pushed him away, it was for good. Did she still care? Absolutely. Lucy knew if he had stuck around with her, she would have gotten them both killed, not just herself. So she pushed him away and stayed in the dark hole in which she lived for a year, hoping to not see the light of day.
Instead, Basil's life took a whole new direction and not one that Lucy would have hoped for. Her point had been made as a grin was ever apparent on his face. "Basil..." What could she say? He was gone.