"Is it normal for a mare to like other mares?"
Fluttershy has never been brave enough to search for the answer to that question. Ever since she was a filly, she has felt as if there was something wrong with her for even having such a question in her mind. She doesn't understand her own heart, her own body and its seemingly wrong desire for the romantic company of other mares. She doesn't understand what, if anything, is wrong with her.
But after all of her life-threatening adventures, after all of the ways her character had been built up, torn down, and changed, Fluttershy feels she is finally ready to ask that question and hear the answer.