Publicly, Rusty will get most blame for it as the president of the DIKs, but Quinn may later throw Sage under the bus for both this and whatever it is she had her set up with this mysterious third party. In order to smooth things over with the DIKs, as it seems this plan of hers will hurt them in one way or another, Quinn could say it was all Sage's doing as she was mysteriously absent from the party and was the one to set up this thing with an as yet unknown guy and she would get Riona to back her up.
Quinn told Tommy that she's wanted to be in charge of the HOTs ever since she got there, so getting rid of Sage would be, in her mind, a logical step in achieving that.