Question

the comment that 'she has a pretty face' makes the girl-​

Answer 1

Explanation:

“She is pretty” - generally people say this when they want to compliment someone and mean it. And while someone should be more than their looks, this is generally a genuine compliment - she is pretty.

“Such a pretty face” - in my experience, this is something you say if you want to imply they don’t have a lot else to recommend them. If you want to suggest they are thick, or vacant, or rude, or unlikely to make it far in life due to some other staggeringly huge social defect, you say “such a pretty face”.