She is proven a good enough actor for a well written role.

Carrie wasn't pushed very far in ANH but she was memorable in a way that none of the female characters in the PT or even the Raiders sequels were.

Around that time there were three big blockbusters with brunette lead actresses and Carrie more than held her own and delivered a performances comparable with Karen Allen and Margot Kidder.

She was great in ESB and not so in ROTJ, the difference being one was a sequel written by people with something to prove (that the first film wasn't a flash in the pan one hit wonder) and the other was a contractual obligation piece captained by a depressed man who cared only about the money.