This is wrong. She had contact with somebody and needs to go into quarantine as a precaution mechanism. Nothing proven yet.

One of her doctors has Corona, she's just in quarantine for now.

She’s in quarantine after having been in contact with an infected person. The article does not mention that she tested positive

I’m reading she is self-quarantining because she interacted with someone who later tested positive.

In quarantine, not confirmed. https://www.cnbc.com/2020/03/22/chancellor-angela-merkel-in-...