Please Don't Feed the Vampire!
She is the reader's pet dog. One story details Fifi biting the packet of red goo inside the Vampire in a Can costume, which transforms her into a ferocious vampire poodle.
One bad ending has Fifi trying to save the reader from the vampire animals from the pet shop, but they overtake the reader and drain all of your blood.
Fifi also appears in the Goosebumps movie. It attacks Lorraine Conyers on her doorstep. Lorraine manages to get away from it. It also appears later in the film when the monsters were going to get Zach, Hannah and Champ on top of the ferris wheel at the abandoned amusement park where it was shown floating near the Body Squeezers.
In her concept art, she has blood around her eyes, one blue eye, and other red. She also has a pink bow instead of a flower.