Plot?

*** SPOILERS ***

(I hope I remember this all correctly...)

A girl about 13 years old lives alone in Rome, Italy, after her politician father commits suicide by gunshot in public. She has a male tutor for school and is happy in her current conditions. However, her grandmother, who is an actress, comes to visit and wants to take the girl back with her. The girl is constantly making nasty and snide remarks to everything the grandmother says. Finally the girl rebels, secretly puts sleeping medication in the grandmother's tea, ties the grandmother atop a bed, and proceeds to torture her with an electric drill and by feeding her peanut butter, to which the grandmother is allergic.

While all this is going on, the girl is a secret vigilante who delivers justice to anyone she thinks deserves retribution, such as a lady she catches stealing wine from a market, or a delivery man she catches committing a hit-and-run accident, or her dentist engaging in an extramarital affair. On her vengeance trips she is accompanied by a tall, growling wolf that wears a cape and a white plastic mask, and walks on two legs, who commits the actual murders, usually by knife. The wolf doesn't seem to live anywhere, and there are hints that the wolf doesn't really exist, but is rather a fabrication of her mind. She usually sets out on these vengeance excursions on her bicycle, wearing white gloves and red boots. Her grandmother attempts to escape from the bedroom by throwing a book through the window to passersby, but in vain. At one point the girl is infatuated with her older male tutor but the tutor has a girlfriend, so the young girl becomes jealous and kills him, too. She also kills her dentist and his illicit lover with a nail gun.

In the end she is presumably committed to a mental institution and is quietly working away in the hospital when she hears somebody making noise by tap dancing outside in the street. The tapdancer is the same person who towards the beginning of the film hit a pedestrian in a hit-and-run accident but whom she was unable to kill. She grabs a syringe and goes outside to kill him, but someone on a passing bicycle (the wolf?) severs both the man's legs with some kind of blade just before she can attack. She follows the wolf into a building, sees the wolf's cape and mask in a bathtub, sticks her head underwater into the tub, and her father appears, with a hint that he's the one who just severed the man's legs outside. They become instant friends and the movie ends with them singing "Que sera, sera" together in the bathroom.

Yes, it's very weird, very bloody, and very offensive, but you asked. :-)