The pair have enjoyed a strong bond since 2021 but there was no quarter given in a see-sawing first set as they swapped early breaks before Badosa attacked Sabalenka's powerful serve in the sixth game, edging ahead with a return that hit the net cord.
"It's tough to play your best friend. She's an incredible player coming back after injury and I'm pretty sure she's going to be back on top very soon," said Sabalenka, who improved her head-to-head record with Badosa to 5-2.
"On court we're opponents, I'm trying not to watch on the other side, just trying to focus on myself and just bring my best game, but anyway they're tough matches against her."
Spurred into action, the powerful Australian Open champion broke back and let out a scream that was met with cheers from fans on Philippe Chatrier court, before she recovered another loss of serve against Badosa.
Last year's semi-finalist hit a monster forehand to go up 6-5 and came up with a delightful backhand slice from the deep en route to closing out the opening set, as world number 139 Badosa reflected on her missed opportunities.
The former world number two, who has struggled with a back problem in recent years while Sabalenka captured two Grand Slam titles, got off to a disappointing start in the second set as her Belarusian opponent reeled off four games in a row.
Sabalenka produced a superb drop to set up match point and the knockout blow came in the form of an unforced error from the racket of the unseeded Badosa but was quickly followed by a warm hug at the net.
"Some days it's actually getting more complicated to play," Sabalenka said of the variety in her game.
"You have so many options, you're thinking too much but today was a day where I wasn't thinking that much, I was just feeling the game and I was trusting myself and just was going for all the shots."
Sabalenka, who is bidding to become the first player since Serena Williams in 2015 to claim the Australian Open and Roland Garros titles in the same season, next faces American 14th seed Madison Keys or 22nd seed Emma Navarro.