What's the meaning of 1 unchanging in relation to a Yes/No question? Is it a Yes?

(To be more specific, the question was: "When she called me, yesterday, she was in country X?". She is my friend, she lives in another country, she called me yesterday, the number displayed on my phone was a number from country X (my country). I asked her about this, she said "it must be the phone, I was home in country Y". I'm pretty sure that when she called me she was not only in country X, i.e. my country, but also in my town. And I think 1 unchanging is a confirmation.)

Not sure how 1 applies to yes/no questions for other people.
For me it's a 'yes', a thumbs-up. A 'correct'.
Once i read in one of the posts here that 1, in some system
or other, means 'no', but in my personal experience it appears
as a yes. In any case, 'correct', so your friend may well be
telling the truth, as in, 1, all correct, all right, nothing wrong
here.

The question here is, was it a land-line? If it was a land-line,
you can be certain where the phone call was from. If it was
a mobile phone, then a mobile from a certain country, will
retain the same 'profile' no matter which country you're in.

the number displayed on my mobile phone was a fix phone number from my country & town. So, from a rational/logical point of view, I am sure she was here. But I used to trust her and I can't accept she lied to me, that's why I tried to find some other explanation ("a problem with the phone" etc). But probably I will have to accept the situation.

Might i suggest you ask about your relationship with her, you know whether your trust is misplaced or not. Afterall thats the real issue. Asking the Yi about phone numbers is a helluva long and difficult way to go about getting to what you need to know, which is 'is this person trustworthy and do i keep her as a friend.'

yes/no aside..

I'm only speculating here but is it possible that the numbers that shown from your country might be that of a relay point in your country, a sort of router of international calls?

Otherwise, if this isn't the case, and she actually is trying to deceive you, I'd take 1 as a potentially dangerous omen.

Trojan, thank you. I know it was not the good question, but I was to shocked and confused to think straight.
Meng, thank you. Usually, when she calls me, the number displayed on my phone is her normal number. 1 year ago she called, it was a number from Belgium, I asked: are you in Bruxelles? She answered "no". But it was a fix phone number from Brussels. And now, this, a fix phone number from my town. Ok, it might be a router, as you said, but a normal answer would have been "yes, it might a number from country X, because I am using a prepaid card I bought there, not my usual sim card".
I am still confused, so I decided to stop thinking about this for a while, and then I'll ask the questions trojan suggested.