it's generally in a situation like starting a fire and failing to report it or in cases where there is a special duty like parent child, or in the example below, foster parent.
http://www.bostoncriminallawyerblog.com/2007/11/massachusetts_foster_mother_fo_1.html
From what I've read, this appears to be a charge of Involuntary Manslaughter, which since there is no battery, is likely a "Welansky" manslaughter charge, meaning wanton and reckless behavior. MA does not have a manslaughter statute. The charge/crime comes from common/case law. Wanton and reckless conduct is distinct from negligence or gross negligence for which, in the common law of Massachusetts, there is no criminal liability.
"Welansky manslaughter," is named after a 1944 case where the owner of a nightclub was convicted of involuntary manslaughter when a fire in his club caused the death of over 400 patrons. That case established that wanton or reckless conduct includes both affirmative acts and failures to act (where a duty to act exists). Such conduct must evidence a disregard for the probable harmful consequences to another and must have a high likelihood that substantial harm will result to another. The law requires that the defendant have knowledge of the circumstances and the intent to do the act that caused the death, and also requires that the circumstances presented a danger of serious harm such that a reasonable person would have recognized the nature and degree of danger.
These are, I believe, the current Jury Instructions on this charge, which sets out the requirements:
http://www.mass.gov/courts/docs/sjc/docs/model-jury-instructions-homicide.pdf
I don't know whether there has ever been a similar case in MA, but none of the articles mention one and I think this may be a first. I can't recall too many high profile cases. The last one was probably the 2011 gun show case which resulted in a Not Guilty verdict. It involved the young boy who shot himself in the head with an UZI at a gun show. The former police chief who helped organize the show was found Not Guilty on the Involuntary Manslaughter charge.
This case did bring to my mind, the Phoebe Prince case. There, her tormentors were initially charged with bullying, violation of civil rights and some other things but they did not go as far as Involuntary Manslaughter, likely because the suicide was not closely enough or causally linked to the conduct. The current case is seemingly much more egregious and directly focused on the suicidal acts with actual direction being given to a person the perpetrator knew was susceptible. I think her actions were so horrendous to the investigators they felt she had to be charged. A lot will probably depend on the exact nature of the messages and her knowledge of the victim. If this is a case of first impression it is probably another reason she was charged as a juvenile.