Now I know that Fluttershy is not actually a Jedi and this is all just head-canon but its fun so roll with it.
She might be fearful rather often. But no Jedi is perfect. However, she often controls her reactions and emotions so as not to upset, hurt or scare others. There is no Emotion, there is Peace.
She has been shown to be able to set aside her own ego and seek out those better trained in an area if an animal needs help she cant give. There is no Ignorance there is Knowledge.
She prefers a calm and well-kept environment around her home. She is really the opposite of Discord in every way but that is why they get along so well. There is no Chaos there is Harmony.
She shows power when it is utterly needed but never before. It's only when others are in danger that she brings her own force to bear on the offender. There is no Passion there is Serenity.
She can be seen to have the ability to control others or at least animals via her stare. Which is a Force power. It is known as Animal Friendship or Animal Bond and allows the Jedi to control and to a lesser degree connect with the animal via the Force which really works with her character.
She also has shown that she is a great mediator and reformer via reforming at least in part Discord in season 3. This is a clear trait of a Jedi Consular. As is her regular willingness to be diplomatic and forgive those that seek it. She is often the voice of compassion and reason and thus I feel her role would fit the Counsular path.
As such I would bet that her lightsaber would be a green hue symbolizing her connection to the force and all that it touches. I would guess her saber style to be Form 3 Soresu the all-defensive form as she is not the type to harm anyone if she can avoid it. So she would sort of be a less combative and wiser version of Kenobi for the move only fans of the series. For those interested in the EU I would liken her to Master Fay.
Her house is outside of the borders of Ponyville proper in the forest where she spends her time communing with nature and its inhabitants. Which is a classic trait of the “old hermit”. So she would also be akin to Old Ben. While she is not against working with others she just does not need to be in the mix all the time. Which again is a Jedi trait One does not seek adventure but does what the Force calls them to do. In short, she is displaying many traits of a Jedi and I find that awesome.