Yo la conozco; es una amiga. I know her (I recognize her); she's a friend
"ella es una chica" means "she is a girl" in Spanish.
Conozco a una persona
That would translate over to: "She is a friend"
Ella es una maestra
Well, first of all, it should be "ella es una doctora" and it means "she is a doctor."
Ella es una chica mala
The feminine form of "un amigo" is "una amiga," both meaning friend in Spanish.
It depends on what kind of vet you mean. If you mean she a veteran, it's, "Ella es una veterana." If you mean she's a veterinarian, it's "Ella es una veterinaria." In Spanish, there is no foreshortening of those words; they say the entire word, all the time.
It means she is stupid but I love her/ care for her
When do you go to your friend's house?
You could say "Eres una bendiga como un amigo."
¿Es él una ella?