Rarity is a fashionista while you are a costume designer and cosplayer. Fashion is what you and Rarity have in common.
You want to return all the good things she and her friends has done. Then Equestrian magic enchants the pendant she gave you and you now have ice powers, much to your concern for troubling her. Rarity can feel your worry and now it's up to her to be there for you to remove the cold feeling within before it consumes you.

The Mane 7, seven relationships, how will each go if Equestrian magic gets involve?

First entry of the MLP Equestria Girls: Guardians