But even after her suicide, the cruelty didn't cease, family members and investigators say. "Yes ik [I know] I bullied Rebecca nd she killed her self but IDGAF" [I don't give a f***]. That message - posted on Saturday on Facebook by Rebecca's 14-year-old persecutor - ended in two arrests.

On Monday, deputies from Polk County in the US state of Florida charged the author of the post and another 12-year-old girl with aggravated stalking.

"That post was the tipping point," Polk Sheriff Grady Judd said. "She forced this arrest."

The 14-year-old started the bullying after she started dating Rebecca's ex-boyfriend, Judd said. The 12-year-old girl was once Rebecca's friend, but the other girl turned her against her. The girls "maliciously" harassed Rebecca while all three attended Crystal Lake Middle School in Lakeland, investigators said. "Several students corroborated stories of both girls bullying Sedwick on different occasions, through name-calling, intimidation, threats to beat her up and at least one actual physical fight," a Sheriff's Office report said.

Judd said neither family co-operated with investigators, so the girls were placed under arrest and charged with the third-degree felony. The 12-year-old was released to her parents because she demonstrated remorse to the judge, but she can't go back to school.

The 14-year-old is in the custody of the Department of Juvenile Justice until her next hearing.

After their arrests, Judd said, the girls admitted the abuse. They remain on house arrest.

Under Florida law, a range of options is available to punish juveniles convicted of felony aggravated stalking.

Brian Haas, a spokesman for Florida's State Attorney's Office, would not talk about the case specifically.

But he said the charge carried a maximum penalty of juvenile probation or placement in a residential-commitment programme for five years or until the 19th birthday - whichever comes first. Judges have a variety of options for sentencing, including counselling and rehabilitation.

According to investigators, the 14-year-old had several arguments with Rebecca via Facebook, as well as verbal confrontations with her at school.

Witnesses said the girl sent messages to Rebecca, calling her ugly, telling her to drink bleach and die and saying Rebecca should kill herself.

Rebecca was attacked in school and later bombarded with hateful messages via a smartphone application including "You're ugly," "Why are you still alive?" and "Go kill yourself."

In February, the 12-year-old was suspended from school after allegedly attacking Rebecca, Judd said. Rebecca's mother decided to home-school her and eventually Rebecca transferred to Lawton Chiles Middle Academy. But detectives found evidence that the bullying continued on her smartphone.

The morning Rebecca took her life, she posted a message to a North Carolina boy who she reportedly met once at the airport. "I'm jumping and I can't take it any more," the text read.

Judd said bullies must be held accountable, especially in today's instant-message, social-media environment.

"As a child I can remember my mother telling me, 'Sticks and stones can break your bones, but words can never hurt you,'" Judd said.

"Today, words stick, because they're printed. And words are as hurtful - and sometimes more hurtful - as sticks and stones. Ask Rebecca's family."