"Yesterday we bought her a doll."
Translation:Ayer le compramos una muñeca.
I don't know about Barry but I wrote "Ayer a ella le compramos una muñeca" and I was told I was wrong.
Duo should accept it. I'm guessing that sentence structure wasn't expected, but it's certainly correct.
In this sentence, "her" is the indirect object and the unstressed complement is le for both masculine and feminine indirect objects. It would be la if the direct object was feminine ("he'll never forget her" - nunca la olvidará a ella).