1) Why wasn't she looking at the limo in both of those frames?
She appears to be looking toward her right up to z202.
2) What was she looking at in Z-148?
She was looking to her right which is where the President's car was.
3) Why did she start turning her head away from the limo and towards the TSBD by Z-141?
She didn't. She is always looking to her right until z202 when she does that major head turn to the rear.