You need only see her. (Is this correct?)

Hi, I know that auxiliary verb "need" cannot be used in affirmative statements, but how about this one? Is this correct?

You need only see her.

I saw this sentence in my dictionary, but I'm not sure if it's correct. Is this really correct?

Thank you!

Viceidol

Hi, I know that auxiliary verb "need" cannot be used in affirmative statements, but how about this one? Is this correct?

You need only see her.

Hi,

Let me quote Swann (Practical English Usage, 3^rd ed., § 366.2):

Need can also have the same present-tense forms as modal auxiliary verbs ... In this case, need is normally followed by an infinitive without to.
        She needn't reserve a seat - there'll be plenty of room.
These forms are used mainly in negative sentences (needn't), but they are also possible in questions, after if and in other 'non-affirmative' structures.
        You needn't fill in a form.
        Need I fill in a form?
        I wonder if I need fill in a form.
        This is the only form you need fill in. (BUT NOT You need fill in a form.)

If we follow Swann, we can use need as a modal verb in an affirmative sentence when a 'non-affirmative' word (such as only, hardly, seldom etc.) gives the sentence a negative kind of meaning. Look at Swann's last example: the sentence becomes incorrect when only is removed.

That said, please notice this usage is mainly British.