Breakdown of Mi hermana prefiere una tostada con plátano y café hecho en la cafetera.
Questions & Answers about Mi hermana prefiere una tostada con plátano y café hecho en la cafetera.
Because mi hermana is already the subject.
Spanish often leaves out subject pronouns when the subject is clear. Here, mi hermana tells you who is doing the action, so adding ella would usually be unnecessary.
- Mi hermana prefiere... = normal
- Ella prefiere... = possible, but usually adds emphasis or contrast
So the sentence is completely natural as it is.