She was one of the first women engineers to pass mechanical examinations of the City and Guilds of London Institute, Royal Automobile Club, and Portsmouth Municipal College.

In her youth, her parents separated and Benest was taken to St. Aubin, on the Isle of Jersey, to live with her mother and maternal grandparents, Eliza and Thomas Powell.

[2] By 1908, she had passed the City and Guilds of London Institute's motor-engineering examination, the Royal Automobile Club's mechanical test, and was a certified driver.

In 1910, she took the Portsmouth Municipal College examination for heat engines and that same year entered a design for a speed alarm in the competition sponsored by Flight magazine.

[4][5] Publishing an article in 1915 in Englishwoman's Year Book, Benest argued that with increasing use of machinery, there was growing need for training women as engineers.

Around the same time, she began attending meetings of the Institute of Automobile Engineers, as an invited guest, since their official bylaws banned women as members.

Gyrotillers were a massive, industrial-grade agricultural ploughing machine used to prepare earth for food production; it is unknown whether Benest operated the machinery or maintained it.