People lose their lives for not paying their gambling debts all the time, and it's difficult to track down all of those dead deadbeats.

Though your suspicions might be right, the head might be someone specifically aimed toward Chiaki.  Then again, she might have been a lot more angry or upset if it was.  It's probably someone she doesn't know, and she put the clues together to get the message.

As Chiaki noted, a conflict is inevitable.  I probably won't write it, but it's coming, and Chiaki knows it.

 

Noted.