Choking usually means got nervous, strangled the racquet so couldn’t hit the ball. That’s not what happened. Barty was cruising to victory and wasn’t ready for the onslaught of winners that come from Anisimova. That’s the opposite of choking.
Barty doesn’t have the power of the other top players, so as she is counter hitting and slicing she always gives her opponent a look in. Keys also went through extended periods of the match where she was hitting clean winners past Ash, who at times couldn’t dismantle the power.
Barty was actually amazing how when Anisimova took control for long periods Ash would just keep counter hitting and never retreated into a defensive mindset. When she led 5-2 in the 3rd, 0-40 with 3 match points, there was no choke as Anisimova elevated her game with 1st serves and was clean off the ground.
Just because a player comes from behind doesn’t mean the frontrunner choked. Momentum changes for other reasons. Barty is as mentally tough as any player in the women’s draw, and often comes from a set down. Choking is a derogatory term that doesn’t describe Barty or her match last night.