Question

She is medium height.对吗？

Answer 1

She is medium height.
这是个典型的错误表达。可以改为：
She has medium height/ She is of medium height.
具体用法参看例句：
She has medium height . and beautiful face.
她中等身材，有一副漂亮的脸蛋。

Round face, bright eyes, darkish skin, of medium height: he knew who that was.
小圆脸儿，水汪汪一对眼睛，黑皮肤，中等身材：他知道这是谁。
He is a man of medium height.
他是中等身材的人。
The man is of medium height.
这男人“中等”个儿。

祝你开心如意！O(∩_∩)O~~

Answer 2

不对，应该加上of.应该是She is of medium height.

Answer 3

你好。最好说
She is （of） average height。 或者：
She is neither tall nor short. / She isn't tall or short.