na-adjectives negative from
HI, there's a little thing i cant understand when conjugating na-adjectives to modify a noun for example:

when i want to say : A quiet person,i attach NA between quiet and person like so 静かな人。

but how do i say : not a quiet person? do i replace the na with じゃない (informal) or do i say 静かな人じゃない。?

almost every lesson that talks about this subject shows an example like this between negative and non-negative

You are a beautiful person. あなたは　きれい　な　人　です。

and for the negative axample:

You are NOT beautiful: あなたは　きれい　では　ありません。

As far as i can tell its a little bit different because in the second example the adjective is no longer modifying the noun "person".

Question

na-adjectives negative from
HI, there's a little thing i cant understand when conjugating na-adjectives to modify a noun for example:

when i want to say : A quiet person,i attach NA between quiet and person like so 静かな人。

but how do i say : not a quiet person? do i replace the na with じゃない (informal) or do i say 静かな人じゃない。?

almost every lesson that talks about this subject shows an example like this between negative and non-negative

You are a beautiful person. あなたは　きれい　 な 　人　です。

and for the negative axample:

You are NOT beautiful: あなたは　きれい　では　ありません。

As far as i can tell its a little bit different because in the second example the adjective is no longer modifying the noun "person".

Answer

a quiet person 　おとなしい人, 物静かな人(静かな人 is OK)
not a quiet person　おとなしい人じゃない、静かな人じゃない、物静かではない、行動的である

e.g.
I am a quiet person.　私は、おとなしい。 or 　私は、おとなしい人です(similar 'shy' )
I am not a quiet person, but I can't be active for some reason. 
私は全然おとなしい人じゃないのに、なぜか積極的になれない。
The door is not strong. ドアは、頑丈ではない or ドアは、丈夫ではない。
My Dad is not stubborn. 父は、頑固者ではありません。 or 父は、頑固じゃない。

Hope this helps.

Answer

I'm not sure about this specific situation, maybe there's some rule concerning people specifically that I'm not aware of (there's a lot of things you avoid saying for politeness sake so who knows), but using a negative na-adjective to modify a noun is not wrong. Or maybe they tend to prefer using positive adjectives when possible. Not quite sure.

好きじゃない人 - (Person I don't like) seems to get quite a few hits on Google (I'm married to someone I don't like, what do I do!! - or a similar context haha).