The description of the three hour, two episode drama is misleading. The daughter doesn't find out her mother is not who she thought she was. Instead she is given a manuscript containing the complete story of her mother's life. Most of the film is what Hayley Atwell's character did in the 40's, with little that makes any sense in the 1970's "present".
Now, the story is interesting, a sort of cloak and dagger British Intelligence outfit that is tasked with convincing the Americans to join the war effort in favour of Europe. Sexy Eva is recruited, trained and unleashed upon unsuspecting foreign agents. However, as many have noticed, the execution of the plot survives only to the most superficial scrutiny. But it is damn ridiculous to complain about the inconsistencies, though, if we liked the movie. It's not like we don't know it's a film.
What does strike as slightly annoying is the length of the feature. Certainly this could have been more concise in the length of a normal film or more detailed and watchable in a three or four episode miniseries. As such, you can't wait for it to be over, waiting for the climactic ending that, alas, doesn't really come. Everything is explained in the end, but with a fizzling finale that holds no power and creates no emotion.
Beautiful Hayley Atwell and Rufus Seawell both made the film bearable due to their performance. Perhaps it would have been better to just discard the 1970's story and just tell the 1940 one from beginning to end. The Americans would have done so, ended the story with her escaping and quickly preparing a sequel. :)