Would you say the same thing if it were Superman?
Or the Flash?
Diana is up there in speed, and Flash has literally evacuated thousands in seconds.
This is the sort of thing I was referring to - lowering Diana's speed for the sake of a story.
In my opinion, if you need Diana to be slower or more vulnerable in order to give a scene impact, then you're not writing the character correctly.
Diana is a powerhouse and shouldn't be shown to be less than that in order to provide emotional impact. Plenty of other top tier characters have lots of impact and emotion without being written as less than what they should be.