i'm feeling  my classmate who is a girl called me cuckoo(but in my language).

Welp. Now you're going to have to retaliate with a whole army of you if someone hits you enough times.

*Sighs* Undelos is probably the only other one here who would get that reference...

Depends on the context.
Don't take it too seriously.
Maybe she saw you do something crazy?

well the only times i've ever said that about someone was either when I was 5, or it's jokingly. 

So maybe you did something funny, weird, or crazy (but not obviously) and she was just commenting on it...

Like X says, it all depends on the context  

But also like he said, 
I'm sure it's nothing and you don't need to worry about it... 

If it is a positive thing, you'd just move on anyways...
If it was a negative thing, you should also move on...
                         (if it WAS a negative thing, and you want to get back at her, I would say to Kill Her with Kindness  ... just be as nice to her as possible (which i feel like you're nice to everyone, I don't know, I just get that vibe from you) and everything will work out fine  )

If you're still worried, let us know what actually happened
and one of us could suggest an explanation.
But again, it's probably not a big deal.
Maybe she wasn't serious?

You ok, Luffy?

well i think i don't know, she always used to bug me when i date her, but she had a bf, and now she's talking like i did something wrong to her, when she started all this, Well i can't do anything, she's 18 now, and she's weird, i think because of my face with zits that's why she calls me.

Mugiwara no luffy wrote:

well i think i don't know, she always used to bug me when i date her, but she had a bf, and now she's talking like i did something wrong to her,

Well if you did nothing wrong, then it's ok.
She's calling you crazy for nothing if you did nothing wrong.

Well she drinks alchol and smokes, so i hate her.