VINA: They found me in the wreckage, dying. A lump of flesh. They rebuilt me. Everything works. But they had never seen a human. They had no guide for putting me back together.
Her injuries were clearly very severe. Even if they could have derived an image of what a human properly looked like from her mind (and as others have said, even that might not be possible if she were unconscious or in a coma) it might not have been physically possible to produce that result from what they had to work with. Also, there's a great deal that general external appearance won't tell you about complex internal anatomy, and there's no reason to think Vina would have had extensive knowledge of the latter. Additionally, the Talosians had become inept even at repairing their own machinery, so why should they be any better at conducting major surgery on an alien species?
As for the Columbia computer banks, those would surely be badly damaged if not utterly destroyed in the crash, and as already said the Talosians would lack the technical capacity to fix them. And even if they hadn't lacked it, would there have been time before Vina succumbed to her injuries? They probably had to act hastily, and crudely, in order to save her life. Cosmetics were likely the least of their concerns.