PC Thompson heard footsteps walking away shortly before he discovered Coles. Thompson was quoted as saying, "I nearly had him. He was only an arm’s length away, and I missed him" but this was written after his death and it's unknown if it was apocryphal statement. Either way, it's not what Thompson stated in his police report.
Had Coles been killed on 30th Sept 1888 instead of Stride, she probably would've been included as a Ripper victim, but of course based on the killer's movements on the double event, Eddowes might have been spared that night.
I've just refreshed my jaded memory by reading Thompson's statement and he heard someone walking away at what seemed to him like a normal speed. I was pretty convinced that I remembered him saying that he'd heard someone running away! Just goes to show that you can't always be sure of what you think that you're sure of!
Obviously 'walking' doesn't point to a killer being disturbed in the act. I still don't think that she can be totally discounted but I agree with Abby that we probably have to list her as an unlikely victim of Jack (also taking into consideration the time gap.)