The Aussies, who dominated England in the recent Ashes series, maintained their winning run despite being pushed to the last over in Hamilton, New Zealand.
Australia's Rachael Haynes was one of the key architects behind her team's victory after scoring 130 runs. Meg Lanning's similarly impressive total of 86 helped the tournament favourites to a score of 310 at the end of their 50 overs.
England fought back with Nat Sciver - who also took two wickets - producing 109 runs from just 85 balls.
Her impressive innings left the defending champions requiring 16 from the final over. However, Jess Jonassen kept her cool and produced a devastating bowling display, conceding just four runs and taking two wickets as Australia got over the line.
On a day to celebrate leg-spin, Alana King claimed three England wickets, and paid her own tribute to Shane Warne - who passed away on Friday - by tapping her black armband.
Haynes starred at the top of the Australian batting order, hitting 130 from 131 balls to put her side in a strong position.
England showed a lot of resilience towards the back end of their innings, led by Sciver, following the dismissal of captain Heather Knight and Beaumont - who made 74 - but were unable to keep up with the required run rate as they started losing wickets.
Beaumont escaped an early scare when she was dropped by Lanning for just four and went on to move past 3,000 runs in the format after bringing up her half-century from 54 balls.
England reached 128 for two at the halfway stage of their innings, but it was the loss of wickets which would ultimately seal the victory for Lanning's side.
Sciver's introduction increased England's run rate, including taking 13 off Ellyse Perry in the 32nd over, but she was unable to build partnerships, with Danni Wyatt making just seven and Amy Jones four.
England were still in with a chance ahead of the final over before an exceptional one-handed caught and bowled from Jonassen to dismiss Katherine Brunt for 25 put an end to their hopes as Sophie Ecclestone also fell from the final delivery as Australia wrapped up the win.