Phoebe Prince’s lilting Irish accent and wide smile made the 15-year-old freshman stand out at South Hadley High School, where she enrolled last fall after her family relocated from a tiny village in the west of Ireland.

Her principal called her smart and charming. A boy invited the new girl to the school’s winter cotillion, a highlight of the school year. But two days before the Jan. 16 dance, Prince died in an apparent suicide, after incessant bullying by classmates at the 700-student high school.

“In a school with that many kids, there are going to be issues,’’ Sergeant Robert Whelihan, a spokesman for the South Hadley Police Department said yesterday. “We are investigating what effects the bullying might have had on the suicide.’’

The bullying included disagreements over teen romances at school, school officials said. And it continued with taunting text messages and harassing postings on Facebook, the popular social networking site.

“The real problem now is the texting stuff and the cyber-bullying,’’ said South Hadley School Superintendent Gus A. Sayer. “Some kids can be very mean towards one another using that medium.’’

Sayer declined to comment on the exact nature of the bullying, but said much of it was done online or by cellphones.

“Apparently the young woman had been subjected to taunting from her classmates, mostly through the Facebook and text messages, but also in person on at least a couple of occasions.’’

In a letter sent to parents, South Hadley High School Principal Daniel Smith said Prince and other students were involved in “public disagreements’’ at the school over dating issues, prompting school officials to discipline students.