"Fast" is too short. I get about 1/5th of a second, and that may be slow due to my finger reaction time on the start/stop button.
Have somebody write something on a piece of paper and hang the paper at the end of a hallway. Do NOT read it and don't let them tell you what it says. It should be written big enough to read from the other end of the hall, but small enough to challenge you.
NOW ... While you are at the opposite end, look down and have them post the sign. Keep looking down and take a step forward. Now look up and let your eyes focus to read the paper. Read it out loud. That is how long a pitcher should be taking before starting any motion.
At that point, the hands come together for at least one second, or the time it takes you to SAY (not think) "one Mississippi" or "one-thousand-and-one".
The step back is legal, but she is illegal in not simulating taking a signal with the hands separated after stepping on.