Final answer:
Abby supports Lauren's claim by stating Isabella was not harmed, indicating answer choice a) is correct.
Step-by-step explanation:
The statement made by Abby (Lilli) is meant to corroborate Lauren's claim about Isabella's safety. Therefore, the correct answer to the question is: a) Abby is corroborating Lauren's truthfulness about Isabella's safety. Abby's statement is a form of support indicating that she was a witness to the event in question and confirms that Isabella was not hurt, thus backing up Lauren's statement.