How does it say correctly with exclamation?
How she looks! or What she looks!
How does it say correctly with exclamation?
How she looks! or What she looks!
Neither can be correct as an exclamation.
There are some idiomatic exclamations which seem similar:
What a goal!
This has the form "What a (noun)". But your attempt isn't in this form.
How about that!
Your examples:
How she looks.
This isn't an exclamation. It is a little noun phrase meaning "The way that she appears". But it doesn't tell you anything about her appearance.
What she looks
Is not correct. You could say "What she eats" (a noun phrase meaning "the thing that she eats") because the verb "eat" has an object. But the verb "look" is intransitive, it has no object. "What she looks" is incorrect grammar.
Now, for your situation. Firstly its rude to comment about people. So often the "correct" thing to do is to keep your mouth shut. In the sort of casual situation you might comment on a girl looking good, there would be lots of unspoken communication. The exclamation "wow", in context, could mean "she's beautiful" or "she's weird" or even "she's ugly"
See that girl by the bar? Wow!
Now suppose you just want to tell someone that a girl looks great. There is no need for some clever idiom.
She looks great!
(But remember, commenting about people is often rude)
Every sentence needs a verb.
Neither of those have one, so they are both not really normal grammatical sentences.
But we say them anyhow! Speakers of English might say "How great she looks!" in conversation, but this is really more like a shortened form of the question "How great does she look?", except it does not expect an answer.
You really need an adjective between "how" and the subject to use that form: "How great she looks!" "How pretty she looks!" "How awful she looks!", and so on.
How she looks!
is also correct, but less common and a little stilted or awkward.
What she looks
is never correct, in any way, and no one will understand what you mean. Don't say this.
We would not use these exclamations in formal writing, only conversation or conversational writing.