Lets take a moment to look at her story and reflect on what happened in the finale.
She was in this afterlife and created for herself a relationship with her son. He was a musician, something that he always wanted to be but was never given the chance to be.
we can theorise that she was somehow given realisation of her life she lead, whether this was giving birth to daniel or touching him, it doesn't matter. What matters is that she recollected EVERYTHING she had done in her life.
She felt the immense guilt of having to send her own son of to his death, she did not want to 'move on' because in this place she could be with him and thats all she ever wanted.
This is backed up by the two separate conversations she has with Desmond. She does not want Desmond to break the illusion that this is not 'real'. Because she has seen everything she knows that all those people were involved with her son. She did not want Desmond to take him and make him fully realise what had happened, and Desmond agreed.... he remarked that 'i won't take him'. But he knows that at some point Daniel might realise on his own and move on.
As a final point....
She had obviously seen her whole life and saw these interactions with Desmond. She knew that Desmond wanted to marry penny and to do this needed to obtain her husbands approval. This was highlighted in Happily Ever After when she remarks - you have EVERYTHING you ever wanted, my husbands approval.
And that was Desmond's whole afterlife - all he ever wanted was Widmore's approval. Something he never obtained in his real life. Of course what drove him and most of the other losties was love. and thats what he needed in order to move on.
absolutely brilliant finale. observations welcome.
thanks for reading.