She envies him, but not for the reason people think.
She can't afford to trust people. Period. Trusting people means lowering your defenses. It means baring the bones of your soul. It means the one thing she loathes the most.
Dependence. The very idea rankles her. Dependence equals trust. Trust means betrayal. Betrayal means begging for a compromise. She can't settle for that. The one and only time she begged, that person simply walked away.
It was a harsh lesson.
But she knows he cares for Sherlock. After all, that's what he does for a living. But just not for her. He would follow Sherlock to the ends of the earth, fusses over him, cares for his welfare. Sherlock looks to him for cues on how to deal with people. What were the words?
Oh, yes. "Bit not good."
Three simple words and Sherlock changes his behavior.
She had asked Moriarty how to handle the Holmes boys. He had launched into a complete monologue about 'The Iceman' and 'The Virgin'. All those flowery words. But those three simples words has an immediate effect on Sherlock. An effect she can never match.
"He'll come after me if I tell him," she had protested.
"I'll come after you if you don't," he had answered. And she believes him.
He appears harmless. After all, he is a doctor. Do no harm, and all that rubbish. But he has power and influence, just not the kind she expected. The kind that held a certain consulting detective in thrall.
He claims they aren't a couple. Maybe (or maybe not) in a sexual sense, but certainly in a spiritual sense.
And she envies that. She envies HIM. She hates him.
Because his power is genuine, from the heart.
It's from Irene's POV, about John.