"She likes me."
Translation:Cô ấy thích tôi.
Well, Vietnamese pronunciation is very complicated that it may be worth more than one article to talk about it. The word "chị" (elder sister) can be used to refer to an older female person in general, and "ấy" is similar to "that", so it is like that woman-who-is-older-than-me. The pronoun that you are taught to use, "cô ấy", is a age-neutral word, though it is not usually used for far older or far younger people, can be understood as that lady.
However, I still don't understand why that word was chosen to appear on the hints for you, because the sentence doesn't suggest that "she" is older, which can lead to confusion because it was not taught.