How is this summoner not ban after this game.

So last night I was playing a normal game, prelevel 30. I got matched with this sivir. after 5 minutes in game she afk. SO to obey her disconnecting she bought a pink ward and placed it next to gromp. for the next 10 minutes she was there. Then she went into mid lane and feed 12 kills. So didnt say a single word in chat. So my though process is, you can int all you want, just dont say a word. Even though my team and the enemy team reported her. She still not ban. It makes no sense how the system works. Fix it.