England open up against South Africa in Perth and expect to have key all-rounder Nat Sciver back from a medial ligament strain.
Captain Heather Knight hoped this result would act as “a little kick up the backside” for her team, who could only make 122 for nine batting first.
Sri Lanka captain Chamari Atapattu then smashed 78 from 50 balls to take Sri Lanka to victory with 45 balls to spare.
"It was a disappointing performance, but I'd rather we got it out of the way ahead of the World Cup,” said Knight.
"Chamari batted really well for Sri Lanka and she just took the game away from us. It might give us a little kick up the backside, which might not be a bad thing.
"We're still in a good place. We've played a lot of good cricket over here and we need to take that into our first game against South Africa.”