While Sylvia in "A White Heron" wants the man's $10 for showing him the location of the bird, she cares more for nature than for people or profit. However, the man's entry into Sylvia's life comes at a time when she is on the verge of puberty, and she has never had feelings of attraction before. In his friendliness toward her, he is manipulating the young girl's naivete to get what he wants: a rare bird to kill and display on his wall.
The answer is a) Sylvia is experiencing falling in love because she is increasingly attracted to the man, but she doesn't follow her physical attraction; instead, she follows her philosophical leanings.