Respuesta :
The author means that Sylvia operates on instinct by following her heart. Her heart operates on instinct means that she goes with her gut. She is one with nature.
Operates on instinct
Think about how animals operate. When a person is "heart to heart" with nature, she is apart of nature acting purely based off emotions and instinct. There is no deep though process or over analyzing of situations. It is purely reactionary and based off instinct. Also, she is definitely not a woodland creature. Mistrusts her dream of love is being used just to trick you with the word love. Tranquility of twilight could be when she feels most connected with nature but it doesn't actually answer the question.