I think the part where she got infected and made pregnant helped me know more about her character.

Tried to watch it twice, both times I fell asleep before the end, what I remember was :


SPOILER:
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;The alien got on the ship, I think it crashed (was startin to doze then), was the girl able to return to earth?
Did the end make sense?
I see the blueray version has alternative start and end, do the make the movie any more interesting/understandable?

Well it might have been a development for her character in particular, but it was just very poorly executed in the storyline as a whole. I'm fairly sure it's possible to do character development so it makes sense in relation to everything else.

Possible for a GOOD writer, sure. But Prometheus was brought to us by one of the writers of Lost, and Lindelof seemed to think that all of the spooky nonsense unexplainable bullshit from that show would work in a movie. Even scarier than that, though, is that Scott didn't object to any of it. Either he didn't know about the plot holes and inconsistencies, or he approved them. Honestly I'm not sure which one is more depressing.

Still, it was an beautiful and entertaining movie, provided you could suspend your disbelief INFINITELY.

edit: Apparently the other writer was John Spaihts, whose only other film work was writing the screenplay for The Darkest Hour, an alien invasion flick with a whopping 16 Metacritic score.