What I picked up in interviews was that Ariadne was something of a therapist for Cobb, so I went into the film with that already in my head. As such, I could watch the entire film and see her playing that role, in trying to get him to come to terms with his wife's death.
The kicker for me was that I viewed the entire film as having been a therapy session for Cobb, a dream of his if you will. The male characters all served purposes, such as Saito being his fear of growing old alone and needing a key to reconcile with himself. Arthur being the part of Cobb's personality that was always logical, dependable, looking out for him, but sometimes missing something...his conscious self, if you will. Eames being the hero, suave and slick whilst also able to fight off an army single handed...what a lot of men hope they have as part of their character. The Professor representing what he was taught (by his father? elders? someone) in terms of guilt and relationships, dealing with feelings - best of intentions, but "I'm just doing what you taught me". Fischer merely served as a distraction (Cobb is going after someone else, not himself) and a means of getting deep enough into himself to get this inception, this seed of self forgiveness, planted so he could move on. I viewed all the characters, and sub-stories, as a means of getting to this point of self-actualization ... however, Cobb couldn't do it on his own.
Enter Ariadne, a non-threatening, small, unestablished character introduced to his psyche who then proceeds to probe deeper into his own issues - to question him and push him deeper into facing himself in ways that none of the other characters have dared to do (perhaps, because they are projections of his sub-conscious?

). She's the one that forces him to face Mal, and tries to explore Cobbs inner secrets and memories, to coach Cobb in overcoming this issue for the safety of all the players (and by extension, himself).
There is a lot of metaphorical imagery to support this take on the film. There is the crumbling world Cobb and Mal built, the use of a 'long journey home' to return to his family, the obvious elevator of Cobb's memories which Ariadne takes to the basement for her real confrontation with Mal, the freighttrain that is Mal's unpredictable and unstoppable influence on Cobb's plans (in addition to being the echo of their lonely world), etc.
So there you have it, my interpretation where this was all Cobb's therapy session under Ariadne's guidance. Also supported by the ending