Fairy Cookie is an S-level cookie that has a magnetic aura which also serves as a shield. Hitting an obstacle will not cause a loss in energy, but will remove the shield and the magnetic aura. The cookie will then require some time to replenish the shield.
Fairy Cookie has a Power+ that gives a shield to another cookie randomly during the game (usually after hitting an obstacle). The magnetic aura is much weaker in other cookies, but the shield remains working perfectly. However, the magnetic aura does stack with Angel Cookie, Fairy Cookie with an original magnetic shield, and Angel Cookie's Holy Feather, creating an even stronger magnetic aura when one or more is equipped and the extra magnetic shield appears. More upgrades will make the Power+ have a stronger magnetic aura and appear more frequently in game.
With least calories and highest fiber content, it's the healthiest Cookie of all. She can even produce oxygen, which keeps the air clean around her. The energy of the forest feeds her protective shield. Those who envy Fairy Cookie say she has strawberry jam of arrogance inside, but you don't believe them, right?
She can be compared to Angel Cookie in terms of power. While Angel Cookie costs less to buy and upgrade, Fairy Cookie has a Power+ advantage and can use her Magnetic Field as a sacrifice to not lose any energy. However, they can be used together (with Cookie Relay, preferably Fairy Cookie first) for a wonderful sweet magnetic experience. You will get the magnetic shield on the relay of the cookie when you have equipped Fairy Cookie as a main cookie.
Her energy is the highest among all other S-grade cookies, with an above average energy of 180 when fully upgraded, a much better rating than Angel Cookie. If she is used with a high level Energy Upgrade her energy bar will go from one end of the screen to the other end.
She could be useful due to her Power+ ability and high energy reserve, and could also be a great asset to gameplay. However, her Power+ does not have a 100% chance of appearing.
This is a decently popular cookie because of the strong Magnetic Aura and high energy.
If she is used as a main cookie, her relay will automatically obtain the aura. However, if she is used as a relay, there is no guarantee that the main cookie will obtain the aura.
You will be able to gain a blue shield on your relay if you use Fairy Cookie as the main Cookie and Fairy Cookie's Power+ triggers while the relay still has the original green shield. The blue shield takes 2 hits to completely break.
Fairy Cookie's Power+ can also activate when she is the current runner. If it activates when she doesn't have the shield, she regains the shield immediately. If she has the shield, she gains a blue shield.
Fairy Cookie's Power+ has a very weak effect on its own, such that some players believe that her Power+ effect only includes a shield and no Magnetic Aura if no Magnetic Aura is equipped, while it actually gives a very small magnetic aura.