Question

Her sister said to her,'You could help her mother with the cooking when you have some free time. '

Answer 1

You could help her mother with the cooking when you have some free time.

This sentence has two different points of view!

Let's set this sentence in first person perspective.

You could help your mother with the cooking when you have some free time.

Now let's put it back into the full sentence.

Her sister said to her, "You could help your mother with the cooking when you have some free time."

Well, now we need to change the beginning to also be in first person perspective.

My sister said to me, "You could help your mother with the cooking when you have some free time."

I hope this helps you and gives you the motivation to try it on your own next time!