Final answer:
The correct family member is ma grand-mère.
Step-by-step explanation:
The correct family member in this sentence is ma grand-mère. The sentence states that 'my mother and my aunt are her daughters and it is not my grandfather.' Therefore, the only family member left that fits the description is my grandmother. The other options, including tante (aunt), soeur (sister), and cousine (cousin), do not match the given information in the sentence.
Learn more about Family members in French