Hello, Joy Lin-- welcome to English Forums.
Both sentences are fine in appropriate circumstances. When we are speaking, we often use #1, but when you are writing, you should use #2, because it is more formally correct: it means I am taller than she is.
Both sentences are fine in appropriate circumstances. When we are speaking, we often use #1, but when you are writing, you should use #2, because it is more formally correct: it means I am taller than she is.
Comments
But generally according to the usage first one is correct