Corrected sentence:
One day, her mother asked her to take a basket of cakes and a jar of honey to her grandmother, who lived deep in the forest.
Why this is better — step by step for an 8-year-old:
- Basket of cakes vs basket of cake: If the basket has more than one cake, say "a basket of cakes." If there is only one cake, say "a basket with a cake" or "a basket containing a cake."
- Who does "her" mean? "Her mother asked her" means the mother asked the girl. If that is confusing, use a name: "One day, Anna's mother asked Anna to take..."
- The comma before "who lived deep in the forest": The comma is correct because it adds extra information about the grandmother (it describes her). It keeps the sentence clear and natural.
- Overall: The sentence was mostly good; changing "cake" to "cakes" (or using "a basket with a cake") makes it clearer and more natural.
Other correct versions you can use:
- One day, her mother asked her to take a basket with a cake and a jar of honey to her grandmother, who lived deep in the forest.
- One day, Anna's mother asked Anna to take a basket of cakes and a jar of honey to her grandmother, who lived deep in the forest.