Your girlfriend is not cool, tell her to chill out.
I wonder how you would say cool and chill out in Spanish. Tu novia no esta amable, dile a relajarse. But that's not really what I want to say, relajar isn't what I mean. Tranquilar maybe? What about cool? How do you say "cool" (not fresco) and chill out? (not relax, it means more like be quiet and sit down and act gracious and not be as annoying). Gracias.
Yes, I've heard Mexicans say "chido/a" to refer to a person.
Ella está bien chida. She's really cool.
In this case, I'm not sure that it would come across the same in Spanish as in English to say "Ella no está chida." It seems odd to me for some reason. I could be wrong.
You might say: Está dando lata. (She's being annoying.) Dile que se tranquila...que se apacigua...que se tranquiliza...
The word for "cool" can often depend on the country in which you are speaking Spanish. In Spain, last I was there, a decent translation for it was "chulo" as in "Esto es muy chulo." ("That is very cool.") Although I'm not sure they would use it in the negative like you want to above, maybe Heidita can help there?
As for chill out, you may not find a perfect translation, although I would probably use "tranquilar" just because I have heard Spanish friends use it in a similar way. Like, if someone was being overly dramatic or getting upset, they would say something like "Tranquilo, no te preocupes." in the same way we might say "Chill out, man, everything's cool."