If she had a wall devoted solely to Sam, I'd be inclined to agree with you. But it was a Winchester wall, evenly divided between Dean and Sam - with a bit of Castiel thrown in. Since neither brother was focused upon, I felt it was implied both were either needed for their skills - being clearly labeled as Hunters on the wall - or were in a some serious trouble.

Also, with no knowledge of the fix-it plan - or it's consequences - it was kind of obvious to me British Lady expected all three to return to the Bunker together. She was prepared to banish Castiel on sight (I'm not sure he's in the 'outfield' rather than confined somewhere by a MoL spell) and confront both Winchesters together. Unfortunately, only Sam was left to take the brunt of her arrogant, Hunter-hating speech for both of them.