The two-times Grand Slam champion wavered slightly as she failed to serve out the match while 5-2 up in the final set.
Romanian fourth seed Simona Halep powered into the third round of the Australian Open on Thursday, defeating British qualifier Harriet Dart 6-2 6-4 in only 77 minutes.
Windy conditions on Rod Laver Arena saw the pair trading breaks of serve at the start of the match before Halep steadied the ship, winning four games in a row before serving out the set.
The two-times Grand Slam champion wavered slightly as she failed to serve out the match while 5-2 up in the final set, but she completed the job at the second time of asking to set up a meeting with either 26th seed American Danielle Collins or Kazakhstan's Yulia Putintseva.
Despite the loss, Dart's performance was a marked improvement on her appearance at last year's Open, when she was beaten by Maria Sharapova in the opening round without winning a single game.