When a lone woman driving on an open country road and carrying cocaine that must reach its destination or else is menaced by a deranged truck driver, she must learn how to survive the day.

When a lone woman driving on an open country road and carrying cocaine that must reach its destination is menaced by a deranged truck driver, she learns to survive the day, the hard way.

This is my suggestion.

So she's a drug mule. Why would I want to sympathize with someone involved in the illicit drug trade? Care whether or not she succeeds, survives?

Hello, this part need clarification (it's what the plot is about): "learn how to survive the day".
The first part is too wordy, and shoud mention a clear inciting event instead of a long description of the situation.