Here's why:
* Transitive verbs require a direct object. The verb "left" is not followed by a direct object. Dara left *something*, but we don't know what.
* Intransitive verbs do not require a direct object. "Grew impatient" and "left" can stand alone without needing a direct object to complete the sentence.
The sentence is describing Dara's actions, not what she acted upon.