Well in The Time of The Doctor Clara encounters a Silent. However she doesn't make any attempt to kill it and she doesn't even recognise it. I would have thought she would, as in Day of The Moon The Doctor inserts footage of a Silent ordering humanity to kill them all into the recording of the moon landing. Now I'd have guessed Clara would have seen the footage of the Moon Landing, as The Doctor says, everyone has, so surely she should have attacked The Silents she encountered