The Blue Fairy is shady. She is always there at critical points for the big moves. Her part in the situation with Rumpel’s mother, giving the bean to Bae, her treatment of Regina, her treatment of the dwarfs, her treatment of the other fairies, taking the empty storybook, not dying from Pan’s shadow, Gideon being stolen, the wardrobe tree takes two debacle. She was there for too much and nothing has been proven about her character except that she doesn’t treat people very well on many occasions, she is willing to use people for her own purposes, Emma, and Bae come to mind, both children, and she is completely unhelpful as a magical ally. Her lack of development does not explain her shadiness away.
Many of the characters lack development, so the ideas about them are still up in the air and there is just too much behind this one. No one has to accept anything or has to move on from the conversation. This is still a viable theory that will never be proven because the character will never be developed because the writers had to move on to different characters because most of the main characters on the show left.