Well, according to chapter 33, she wanted to erase her twin sister [Tsubasa Uehara] and she even told her boyfriend, Midori along with the class. She was afraid that Tsubasa would take her mother from her since the divorce. This makes Tsubasa devastated since she loved Arisa so much and thought they were always happy. Akira Manabe was also in a total shock after seeing Arisa with a rude behaviour. He fell in love with Arisa before the accident but forgot after Shizuka committed suicide. Akira becomes Tsubasa's only ally and is slowly falling for her.
Midori saves Tsubasa but he is actually Arisa's ally and is only pretending to be nice to Tsubasa. Tsubasa is actually falling for Midori which can also be a reason why Arisa is really angry.
Answer - Yes, she's bad but could be good
arisa
Arisa Mizuki's birth name is Mizuki, Arisa.
Arisa Cox was born in 1978.
Arisa's birth name is Rosalba Pippa.
If you are talking about the shoujo ARISA then there is no anime coming out for it --- No one in the company has decided to start an Anime for Arisa.
Arisa Takada was born on 1987-02-17.
Arisa Andō was born on 1961-03-05.
Arisa - album - was created on 1991-12-04.
Tohru first meets Arisa in chapter 39.
Arisa Ogasawara was born on September 30, 1980, in Japan.
Arisa was born on August 20, 1982, in Genoa, Liguria, Italy.
Arisa Mizuki was born on December 5, 1976, in Tokyo, Japan.