With those firms involved, the attorney fees may well exceed the cleanup costs.
If I recall correctly, the law at the time set a cap on cleanup damages at $75 million. That being the case, BP has a hammer to use against Obama if the DoJ gets too aggressive. BP could say they will pay the government the $75 million and let Obama figure out how to clean it up for that price.
Wouldn’t be surprising if she was picked to negotiate something along those lines, stranger things have happened. Also I’ve read that BP was a large donor of Obama.