What did the narrator learn about herself after destroying Miss Lottie’s marigolds?

From the text:

"As I gazed at the immobile face with the sad, weary eyes, I gazed upon a kind of reality which is hidden to childhood. The witch was no longer a witch but only a broken old woman who had dared to create beauty in the midst of ugliness and sterility. She had been born in squalor and lived in it all her life. Now at the end of that life she had nothing except a fallingdown hut, a wrecked body, and John Burke, the mindless son of her passion. Whatever verve there was left in her, whatever was of love and beauty and joy that had not been squeezed out by life, had been there in the marigolds she had so tenderly cared for."