In the end of Skyfall, M says that she did get one thing right. By my understanding she meant Bond.
But, what exactly did she mean in that dialog?
She meant that she was right in trusting Bond to do the job, even if he failed the tests, and failed in the other choices.
M accepts her failure a little while before they get prepared for Silva to come.
M: I f**ked this up, didn't I?
James: No. You did your job.
She was right in one choice and James Bond proved her right. That's all she meant by that dialogue.