The African was in the lead round after round and brought home a great first place with a great time. The attack of her fellow countrywomen Gladys Jerotich Kipkemoi (a season's best 9:16.21) and Lydia Jebet Rotich (a personal best 9:18.03) came too late.
"I ran too fast in the middle of the race and in the seventh lap I felt such a pain in my chest", said Cheywa.
"I was worried that I could not finish the race. That means I am surprised by the final time."
Cheywa and Kipkemoi both now have 6 diamond points.
In matching her season's best of 50.34 seconds, Amantle Montsho (BOT) won the 400m women during the Bislett Games in Oslo today.
Jamaica's Novlene Williams-Mills finished second (50.43) and American Debbie Dunn was third (season's best 50.75).
With this victory, Montsho took the lead in the Diamond Race; the winner of the first race, Allyson Felix (USA) was not in the starting grid in Oslo.
"For the first time in my career I won such a big meet", Montsho said. "I knew that I'm in shape and to have strong opponents in the race was my big motivation.
This season I have enough power. My goal is the Commonwealth Games in October, but I hope to break the 50 seconds soon again."
Like in the women's steeplechase, the race for the diamond in the men's 400m hurdles men could become especially tight as well. Clement Kerron (USA) won in 48.12 and took revenge against his compatriot Bershawn Jackson.
The winner of the race in Doha clocked second in 48.25. Third was Briton David Greene in 49.05 seconds. Kerron and Jackson lead now the overall with six points both.
"48.1 is a great time, I'm satisfied", Kerron commented. "This ist my first appearance at Bislett, I will have good memories! In the last couple of days, I was working on my curve before the finish.
Today, I did 13 strides all the way round and I was confident that I would win entering the final 100m. So far, the season went good for me!"