Final answer:
The provided text excerpts do not contain information about Malú's abuela leaving Mexico, so it is not possible to determine her age at that time.
Step-by-step explanation:
The question 'How old was Malú's abuela when she left Mexico?' does not provide sufficient context or information from the text excerpts to ascertain the age at which Malú's abuela left Mexico. The provided excerpts mention various individuals and their experiences related to crossing borders or their life in Mexico, but they do not clearly mention a character named Malú or her grandmother. Therefore, without additional context or information, it is not possible to accurately answer this specific question.