Here's why:
* Participle: "Sighing" is the present participle of the verb "to sigh." Participles act as adjectives and describe nouns.
* Phrase: "Sighing loudly" functions as a single unit that modifies the noun "Kristen."
* Purpose: The phrase describes the manner in which Kristen accepted her punishment.
Let me know if you have any other questions about participial phrases!