Coco Gauff has been in a very poor form lately, struggling to serve and to hit a forehand.
In her first match against Uchijima she hit 21 double faults and 74 unforced errors. Her forehand was atrocious and when she tried to hit with power, she very often sent the ball out. She won because of her great athleticism and because of Uchijima choking.
In her second match against Sakkari, she tried to play slowly and carefully in order to avoid mistakes. She just pushed the ball into the other side, letting the Greek control the rallies. It worked out because Sakkari turned out to become an error machine.
It won't be the same against Bencic, because Bencic is much more solid player and doesn't usually do quite as many unforced errors as Sakkari. And she is much better capable of taking advantage of slow-paced balls hit into her court side in case Coco decides to play like that again. And if she tries to hit with power, she will do a lot of errors, so both ways she loses.
No way she reaches a WTA1000 QF with this serve and forehand.