A pretty late response, sorry... but when Heather gets knocked down, you pretty much have to wait it out for her to recover and get back up. I tend to push the < side to side > buttons (not sure what they are in PC controls) to try to help her move, but I don't think that makes her get up faster.
In any of the games, though, pushing those buttons quickly & repeatedly will help you wriggle and push your way free when a monster has grabbed you or pinned you down (although some newer games give a different button prompt for that instead).
are you referring to the ones that makes your player move to either the left or right side?
if so,thanks for the help!