only she knows about it vs only she know about it

Some examples from the web:

• I'm only thankful she knows nothing about it.
• And I only know about it because I saw Bryan creating a file on it.
• We only know about it because of this, this and all the other photos we found in his flat.
• I only know about my own kind.
• The public only knows about three.
• Writers only know about the human soul.
• The street musician only knows about two chords.
• Only studio publicity knows about it.
• Only you know what has happened, you only know about it because we told you.
• Leo's bags were on the plane, so she tells 'em what to look for, things that only she would know about.
• And I guess for you, it is easy to forgive that because you've only know about me for 16 months.
• And he only knows about my secret, not yours.
• All right, I'll go in first, since she only knows about me.
• If I'd only know about this lady before... she would've been included in the invitation tonight.
• The Competition DG has produced a package on financial compensations, which I only know about through journalists, and essentially these texts completely ignore the advice and requests of our Parliament.
• We only know about the stock that has been sold, which is not far off 160 grams.
• Sestus not only knows about the dragoons, he is one of them.
• It's kind of a setup, only neither party knows about it.
• The only people who know about it are you and Jason.
• And he's the only one who knows about it.

Some examples from the web:

• I'm only thankful she knows nothing about it.
• And I only know about it because I saw Bryan creating a file on it.
• We only know about it because of this, this and all the other photos we found in his flat.
• I only know about my own kind.
• The public only knows about three.
• Writers only know about the human soul.
• The street musician only knows about two chords.
• Only studio publicity knows about it.
• Only you know what has happened, you only know about it because we told you.
• Leo's bags were on the plane, so she tells 'em what to look for, things that only she would know about.
• And I guess for you, it is easy to forgive that because you've only know about me for 16 months.
• And he only knows about my secret, not yours.
• All right, I'll go in first, since she only knows about me.
• If I'd only know about this lady before... she would've been included in the invitation tonight.
• The Competition DG has produced a package on financial compensations, which I only know about through journalists, and essentially these texts completely ignore the advice and requests of our Parliament.
• We only know about the stock that has been sold, which is not far off 160 grams.
• Sestus not only knows about the dragoons, he is one of them.
• It's kind of a setup, only neither party knows about it.
• The only people who know about it are you and Jason.
• And he's the only one who knows about it.