Screen time for big actors

It's so strange how Jennifer Jason Leigh was in this film. And her character was basically nothing, and she had barley any lines. That role could have been ANYONE, and definitely someone with less talent than Jennifer. I am wondering if she is good friends with the director/producer or someone in the film because obviously noone in this film probably got paid what they all deserve--they all are fantastic and basically A list actors doing a clever independent. But I am surprised they put Jennifer into that role. Why not the role of Gina? Was she doing them a favor because if people see her name in it they will be more interested in seeing it? She has a really good acting reputation in Hollywood, is Oscar nominated and won lots of awards etc etc and also very talented. So I'm thinking she did it as a favor. Even James Marsden wasn't in the film that much and also could have done it as a favor because of how small the role actually is in terms of screen time and acting ability.