Grace Brockelsby, 19, was struck by Marc Gibbins' HGV on a dual-carriageway and later died in hospital.
The woman, described by her family as "gentle, kind-hearted, caring", had just a few hours earlier been at hospital for a psychiatric assessment following long-standing mental health problems.
At her inquest today, it was heard that the Japanese anti-anxiety drug not licensed in the UK may have affected her cognitive ability at the time.
While Paul Smith, area coroner for Lincolnshire, said Grace deliberately walked out in front of the lorry, he gave a narrative conclusion. He said there was not enough evidence to suggest suicide.
“I record that her intention in so doing cannot be determined to the required standard," the coroner said.
“Drivers are sometimes forgotten victims in cases like this and he has my sympathies as well as the family."
Boston Coroners Court was today told dashcam footage captured the moment of impact.
It showed Grace looking towards Mr Gibbins' HGV, burning her back and supposedly bracing herself for impact near Boston, Lincolnshire, on June 5.
In written evidence, Mr Gibbins, 48, said: “Up ahead I could see a blonde-haired female wearing a coloured top, standing on the left.
"She was on the grass verge and looking as if she was waiting to cross. She was looking in my direction.
“As I was almost level with her I saw her step out in front of me. I could not do anything in time to avoid hitting her.”
He brought the lorry to a stop as quickly as possible.
Mr Gibbins added: “I was in severe shock. I knew this was an intentional act as the girl had waited for me to be so close to her and was looking in my direction as she stepped out.”
A collision investigation found that the lorry was travelling at or about the 40mph speed limit and Mr Gibbins was not at fault in any way.
He had stepped on his brakes, sounded the horn and flashed his lights.
The inquest was told that Grace had gone into the road when he was 26 metres away. The lorry would have needed between 41 and 59 metres to stop.
Grace had suffered from mental health issues for about five years, including anorexia. She had twice been sectioned after intentional overdoses of prescribed medicines.
The teenager regularly told mental health care professionals of her frequent suicidal thoughts.
However, she had shown no sign of ever acting upon them and had expressed that she would not because she did not want to upset her family.
Lisa Teague, speaking on behalf of the family at the hearing, said: “I think all family and friends present here today do believe that Grace did intend to take her own life.”
Speaking previously, Grace's dad Lee said: “She would enter a room and her presence would be known immediately and filled with life and laughter.
“She had the biggest blue eyes and an awesome devilish laugh.”
And her mum Thea Cox said: "Grace touched so many hearts. She was such a gentle, kind-hearted, caring, elaborate, quirky, infectious individual.
"She was unique and inspirational - there are no words to describe how amazing she was."