Liberty is actually very articulate. I think she is a lot more intelligent that she sometimes sounds - if you listen to her words. She has a very girly, almost childish tone of voice though which makes her come across as a bit dizzy and simple. If she had Priya's accent she would be taken a lot more seriously.
I think she is very perceptive. She knows something is off with Jake. It is so late in the day though - she mentally must be thinking 'do I just go with this to the end of the show and then deal with it'.
I agree with the PP. I think Jake is planning on a last minute 'cold feet', lots of crying, lots of drama, lots of soul searching with the boys. He will then suddenly redeem himself, realise Liberty is the woman of his dreams, he just felt 'so vulnerable' as he has never felt like this before. He will then get down on one knee and declare he 'loves her' (in a suitably staged and choreographed manner) just in time for the final vote. Perfect romantic comedy ending.