( CNN ) -- Authorities are investigating whether it was an extreme case of bullying that led to the death of a 17-year-old student in Argentina , after she was attacked by two women and another girl last week . Naira Cofreces died Sunday of multiple injuries , including bruising to the left side of her brain , officials said . `` First there was a verbal altercation and then she was kicked , punched and Naira 's head was smashed against a wall , '' Judge Maria Laura Durante told Telam , the Argentine state news agency . The judge also said this is a case of `` aggravated homicide because there might 've been premeditation . '' Officials say the teen was attacked last Wednesday at about 10 p.m. , after leaving the night school she attended in the city of JunÃ­n , about 260 kilometers ( 161 miles ) west of Buenos Aires . Her attackers , ages 17 , 22 and 29 , were waiting for her after school . The two younger ones were her classmates . All three have been arrested and charged with aggravated homicide , authorities said . `` There 's no clear motive . We have testimony that suggests the motive could 've been another girl or because they ( the victim and her friends ) acted as if they were more beautiful than the rest and dressed better than them , '' Durante told Telam . A close friend of Cofreces told CNN affiliate Channel 9 the dispute started over differences that the victim and her alleged attackers had over looks and demeanor . `` She ( one of the attackers ) would tell her that she had a snobby face , an old woman 's face , that she thought she was more beautiful than her and that she walked as if she were a model . That 's how the whole problem started , '' said the friend , who was not identified because she 's a minor . Cofreces went home after the attack , but was taken to Agudos General Hospital the following morning . `` She came the day after she was beaten up , we did a tomography and discovered a big hematoma on the left side of her brain , so we decided to operate , '' Dr. Carlos Garbe told Telam . A new tomography revealed more bruising of the brain . leading to a second surgery . `` After the second surgery , she continued to show complications which worsened until she died , '' Garbe said . Cofreces was pronounced dead Sunday night , four days after the attack . The incident has caused a public outcry in Argentina . Nestor Ribet , education undersecretary for the Buenos Aires Province , says he has sent counselors to JunÃ­n to work with students and their families at the school where the attack took place . `` We 're talking about the death of a 17-year-old child . Nobody can explain why this happened , '' Ribet told Telam . `` There is really nothing that can explain this . ''
Two of Cofreces ' alleged attackers were her classmates , officials say . Comment: A friend said one of the alleged attackers told the victim she had a snobby face .