The opponent played over her head with excellent defense. However, it's impossible to beat Zhang Yining who is far more experienced. Let's face it One doesn't expect to beat the best of the bests. 张怡宇是国宝 China's National Treasure.
Pak's chopping is too high most of the time, leaving defects for Zhang to attack by "pulling" (half top spin half smashing). Both players' servings are lack of change. Pak's choppings are lack of change of spinning, so relatively easy for Zhang to attack.
Zhang is varying the spin in each loop. The slow loops are all full of disguise. Park had a few chops earlier on that went straight down the net, so she erred on the side of caution, now popping up higher. The other option was to move around and use the pips on the backhand, but that puts her out of position so she can only do that with discretion.