So lets say Serana actualy had a choice during the Coldharbour ceremony. Does anyone actualy believes that she would get away or that Harkon would even allow her to escape. The guy sacrificed 1000 souls for this. I my self doubt she would be allowed to escape from the ''Family event''. What are your thoughts?

Why would she even want to? She considers vampirism a gift unless the dragonborn corrupts her mind with thoughts of being mortal.

Had to ask this after the last thread got locked eh? And now we can't make a second one .

To answer your question, No I don't think Harkon would allow his daughter to refuse being pure-blooded.

She considers it now and even then in DW mission before entering Soul cairn she question if that really what dragonborn wants. But the question is about thousand of years before the time of Alduins return.

It's implied by Valerica that Serana had no choice, as it was 'expected of her'.
On a side note, while Harkon claims his family acquired their vampirism by sacrificing a thousand innocents, Valerica says she and Serana took part in a ritual regarding Molag Bal's summoning day, claiming the few who survive the ordeal emerge as Daughters of Coldharbour.

Perhaps Harkon made his story up to cover up the actual event.. o_o'