"She needs to change."
Translation:Cô ấy cần thay đổi.
Can you use just "thay" or "đổi " in thia case. I get very confused when two words that have same meaning by themselves are put together to make a word with the same meaning.
thay đổi is intransitive so it can stand alone while if you just use thay or đổi you need to specify what. Vietnamese very often glues together two synonyms often a Northern and Southern word combined like: chăn mền (blanket), muỗng thìa (spoon) and ly cốc (glass).