A teenage girl who leapt to her death had lost her boyfriend to a drugs overdose months before, a fatal accident inquiry heard.

Neve Lafferty, 15, and Georgia Rowe, 14, fell more than 100ft from the Erskine Bridge into the River Clyde in October 2009 in an apparent suicide pact.

Neve's mother, Collette Bysouth, told an inquiry at Paisley Sheriff Court that, after the death of 16-year-old Jonny McKernan, her daughter had tried to kill herself twice.

She said it was unclear whether Jonny's death, at his home in February 2009, was deliberate or an accident.

At the time, Neve was staying at the Good Shepherd Centre secure unit in Bishopton but her mother believed she should be allowed out to spend time with Jonny's mother and sister, with whom who she was apparently "very close".

Ms Bysouth said: "I took her to his house to be with the family. I left her there for an hour, and when I came back she asked to stay longer, which I allowed.

"What I didn't know then was that Jonny was still upstairs in his bed and Neve had been allowed to go up and kiss him goodbye. I didn't agree with that."

The hearing was also told Neve – always "Daddy's girl" – had seen her father being stabbed three years earlier, during a fight.

She told the hearing that in 2006, when Neve was about 11, she was staying at her father Paul Lafferty's house in Helensburgh when a fight broke out.

Neve told her mother she had witnessed an argument, and was ushered into a bedroom.

Ms Bysouth, said: "She told me she heard all the screaming. She saw all of the chaos and she saw Brian lying there.

"He is the man who died that day. She saw her father with stab wounds and covered in blood."

The inquiry heard Mr Lafferty had 17 stab wounds and was in intensive care for around four months. He was later tried for the murder of Brian Folan but was found not guilty.

Ms Bysouth said she later found a letter under Neve's mattress, after she had cut her own wrists, which said she had "never gotten over" what had happened to her father.

Neve wrote: "I always knew he would die soon but I had to be first." The inquiry heard Neve believed her father would "drink himself to death".

Ms Bysouth said Mr Lafferty went to stay with a friend in Copenhagen to "get out of Helensburgh". With her boyfriend dead and her father gone, Neve felt as though she "had no-one left".

Ms Bysouth started to break down as she said: "I think she blamed me for her being in care, and for the fact she wasn't with Jonny the night he died. She blamed herself."

The inquiry, before Sheriff Ruth Anderson QC, continues.