Great Winky voice -- and a believable scenario overall. I've never thought that Minerva would be so easily hoodwinked as to give up on Severus, so it makes sense that she'd find a way to look after him. And of course Severus would eventually notice Winky's behavior; you don't survive as a double-agent without paying careful attention to all that goes on around you.
Here's probably my favorite paragraph:
She saw how he observed the other professors with a terrible look of longing in his eyes, like an elf who had been banished from its home but still watched its family from afar. She saw him huddled at his desk with his hands covering his face. He slept little and barely ate. He appeared, in short, as bereft as she had been when she was dismissed from the Crouch family's employment.
For a "non-intellectual," Winky is pretty smart! She's observant and knows how to interpret what she sees, making perceptive use of her own experience.