Maybe like she said, she heard a shot.
Seriously, that's your argument? She was running at a fair gallop and was trying to process what she heard and you expect her to stop on a dime, you try it.
No. My argument is that the evidence is consistent and overwhelming that the first shot was much later - just after the VP car had completed the turn (VP car occupants) when the VP security car was completing the turn or parallel to the TSBD (VP secuity car occupants), or a bit after z186 (photographers Robert Hughes and Hugh Betzner) or just before z202 (Phil Willis) or about when the President was opposite the Thornton Freeway sign (z200 - TE Moore,. Linda Willis). There is no evidence that conflicts with that evidence. So the basis for your conclusion, which conflicts with all that evidence, may not be reliable.
Rosemary Willis said, many years later, that she recalls stopping and turning her head in the direction of the sound and seeing pigeons fly from the top of the TSBD. She did not say how fast she was running when she heard the shot. She did not say whether she had started to slow down before the first shot. I doubt she would have remembered such fine details. She just said she stopped and turned to look back to where the sound had come from. She is running trying to keep up with the motorcade and then starts slowing down when she reaches the grass - but she does not stop until z199. She turns her head in the direction of the TSBD rather suddenly and noticeably from z202-206. A shot at z195 is consistent with that shot timing. It may also be consistent with a shot at z155 and a slow reaction. The zfilm by itself does not provide conclusive evidence one way or the other.
You have to look at all the evidence. And when you do, you have to conclude that the witnesses in the motorcade, along Elm St. were either not independent and, for some common reason said that the first shot was 3 seconds after when it really was and they simply forgot that JFK kept waving for 3 second before the next shot, OR they were correct that the first shot was after z190.