This must be an idiom, right?
That means "she has got a sad face"
What's wrong with> ela colocou uma expresão triste
That wouldnt make sense....
What's wrong with "Ela colocou uma...
Paulenrique, I didn't read down before posting. Well, how would you really say "She put on a sad face." or can it not be said?
Yes, then we say "ela ficou com uma cara triste" ;)
You could also say "ela fez uma cara triste".
ela vestiu doesn't work either?
you translate "to put on" as vestir just when it is related to clothes.
Do Brazilians use the verb colocar in this manner: "Ela se coloca uma expressão triste"? Is this correct?
No, that would not be right,
Could you use fazer with an expression?
Surely, it's very common, specially if you use "cara" (face) instead of expression.