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
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.
The feminine form of "un amigo" is "una amiga," both meaning friend in Spanish.
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."
Yo no te conozco pero ustedes hacen una linda pareja.