The Slytherins kept to themselves.  Malfoy and Goyle had barely been seen in the common room, mostly just as they were passing through to go to their room.  Parkinson stuck to their shared room, but Greengrass would occasionally join Hermione and Padma’s studying.  Zabini and Nott were in the common room for a few hours that day, eventually leaving back to their room.  There were two other Slytherin girls Hermione didn’t know well, but who seemed to stick to Parkinson, seemingly less because they were friends and more because of the protection Parkinson provided.