A whitebaiter who died from head injuries after falling from her bike was drunk, a coroner's finding reveals.

Diana Perriton died in a helicopter on her way to Christchurch Hospital in September last year after falling 1.5 metres onto a road in Westport.

The findings of Coroner Christopher Devonport say 50-year-old Ms Perriton was drunk at 1pm after drinking wine while whitebaiting with her partner William Barnsdale.

Her blood alcohol reading was 257 milligrams of alcohol per 100 millilitres of blood - more than three times the limit to drive.

"The high blood alcohol level in Ms Perriton's blood is likely to have affected her judgment and impaired her ability to control her bicycle or her reactions," Mr Devonport said.

In addition to her head injuries, Ms Perriton also suffered spinal injuries.

Witnesses were at odds over whether she was wearing a helmet and Mr Devonport said the lack of a helmet, or one that was not properly secured, failed to reduce her injuries when she fell on September 9.