The pupil at Braunton Academy in Devon was among 95 pupils who attended the annual leavers’ party at Barnstaple Hotel on Thursday evening.
They enjoyed non-alcoholic drinks followed by a two-course meal and then a disco before leaving at 11pm.
The girl was involved in a collision at around 12.40am on Friday as she walked along the A361 and died at the scene.
The road was closed in both directions at Trimstone, from Dean Lane to A3123 – Mullacott Cross Roundabout – and reopened later on Friday morning.
A spokesperson for Devon and Cornwall Police said: “Police are investigating the circumstances surrounding an incident that lead to the death of a teenager in North Devon.
“Police were called at around 12.40am on Friday, June 28, with reports of a collision between a Nissan pick-up and a 16-year-old local girl.”
Barnstaple Hotels group HR manager Andrew Mosedale said: “Our condolences go to the family. We have done some checking and the young lady was at the prom for the whole thing which finished at 11pm.
“We don’t know what happened after that or what provisions were made to get themselves away and back to their homes.
“Obviously we are very upset by the news and we will be talking to the school to see if there is anything we can do in the future or currently to assist the school and family to move forward.
“When there is a prom we have bar staff and security staff and have bag searches, but I do believe there are quite a few after parties that go on in other peoples’ houses but we don’t know what they do when they leave us.”
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