Atonement and redemption are often confused. One ability to atone does not guarantee redemption. Do you think the author offers Briony redemption?
I agree with other editors in arguing that Briony does not receive redemption by the end of the novel. She certainly makes her atonement in the form of the novel and revealing the story behind the deception that had such tragic consequences. However, she remains bitterly haunted until the very end of her life by what she did, showing that redemption was something that she chose not to accept.
The ending reveals that Briony believes she is not being offered redemption. All she has is her atonement. The one gesture toward redemption extended by her life is that she is to end her days surrounded by her extended family and with less and less of a recollection of her past..
Atonement means that you make amends for your misdeeds. Usually, it involves more than just punishment. The person has to admit wrongdoing and express remorse, in my opinion, for true atonement. Redemption does not necessarily result from atonement. You can atone without being redeemed. Some people are irredeemable.
Any reference to "the author" in this novel is a confusing thing, isn't it, since there is an author who narrates as well as a character who authors this writing. It is true that atonement is different from redemption, and it seems to me Briony does her best to atone for her selfishness and sins. Redemption may be more difficult to prove. You ask if McEwan offers her a chance for redemption, and I suppose the answer must be yes. He makes the offer by allowing her to write her story and reveal both her sins and her repentance. The larger question for me is whether Briony accepts the redemption she is offered. I think perhaps she does not. a
This question is opinion-based, which means that provided you give support for your response, you cannot be wrong. However, it also means that others may disagree; having said this, the following is my opinion.
Briony considered her story atonement for her actions, meaning that by telling it, and by altering the ending to something pleasant, she was able to correct the wrongs she had done. Unfortunately, it is highly unlikely that Briony felt redeemed. Due to the nature of their actual ending--with both characters dying and never having the opportunity to experience the relationship they wished to develop--it is more likely that Briony believed she had done the best she could under the circumstances, but only experienced deeper regret; in writing their love story, she gave herself a view of what they could have had, and the fact that she had been the one to prevent it is only more painfuul.