Alec completely believes that the bear can understand her. Why not?

"I suppose you should also ask your roommate too," he said. "Unless you're lucky enough not to have one."

While he understands the necessity of roommates, it doesn't mean that Alec has to like the idea. He spent most of his life without a roommate - only sharing a room with his twin sister when they were in the nursery. Then he got his own room.