Maybe when Charlize took Idris to her room she used her Andriod hypnotism to make him think they had sex and so she wasn't an Android?
There seems to be a lot of problems with the plot of this film, too many whys that don't fit with what normal people (or even the chracters we met) would do in those situations. Is it lazy writing that made it so implausible or a need to satisfy the Hollywood desire for action, aliens and some rousing moments of human spirit that were shoehorned into a screenplay making it appeal to the masses but ultimately a very flawed film.
all this effort by us to explain what happened, how and why it happened is surely something that a good film doesn't make you do, I'm all for a film leaving something unsaid so we have to make our own decisions, but there is too much in this one for us to really come to any kind of consensus on.
I can understand what Shane means, I really enjoyed the film when I watched it, but after seeing all the plot points exposed I feel it isn't as good as I thought it was. But I still enjoyed it at the time.