The defending champions have gone with an unchanged side for Thursday's clash at St George's Park in Gqeberha.
Left-arm spinner Jess Jonassen, who had made way for legspinner Georgia Wareham for Australia's second game, against Bangladesh on Tuesday, remains on the bench.
Wareham, the player of the match during Australia's eight-wicket win over Bangladesh with three wickets, will share spin-bowling duties with Alana King.
Sri Lanka, who are yet to get the better of Australia in international cricket, have left out offspinning allrounder Kavisha Dilhari.
In the last of the six previous T20I fixtures between the two sides, Sri Lanka ran Australia close but Lanning and the newly retired Rachael Haynes eventually took them over the finish line in the final over of the chase during the 2020 T20 World Cup group-stage fixture.
Openers Harshitha Madhavi and captain Athapaththu, both in form, could challenge the Australian attack despite the overcast conditions at St George's Park.
Australia: Alyssa Healy, Beth Mooney, Meg Lanning (c), Tahlia McGrath, Ashleigh Gardner, Ellyse Perry, Grace Harris, Georgia Wareham, Alana King, Megan Schutt, Darcie Brown.
Sri Lanka: Chamari Athapaththu (c), Harshitha Samarawickrama, Vishmi Gunaratne, Anushka Sanjeewani, Nilakshi de Silva, Maisha Shehani, Oshadi Ranasinghe, Ama Kanchana, Sugandika Kumari, Inoka Ranaweera, Achini Kulasooriya.
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