Sri Lanka won the toss and chose to bat, losing an early wicket before captain Chamari Atapattu steadied the ship with an entertaining 33 before holing out to square leg, a ball after hitting Radha Yadav for six.
Kavisha Dilhari chipped in with a breezy unbeaten 25 in their 113 for nine, but India's spinners were the stars of the show, led by Yadav who took a career-best 4-23.
Teenage sensation Shafali Verma was again the standout batswoman for India, partnering first with Smriti Mandhana (17) then Harmanpreet Kaur (15) to rattle off 86 of the runs in the first 10 overs.
She was run out for 47, but had set up India for another win and they raced to their target with 32 balls to spare.
"It's really important to continue the momentum when you're winning games," said Indian skipper Kaur.
"You really work hard, so you can't afford to lose that momentum. You can't bowl the same pace and lengths on these wickets, so you need to keep rotating the bowlers."