Toxic player

In on of my recent matches I had a nami jungle. This isn't the worst thing to happen so I don't think much of it. However, the rest of my teammates start saying "report nami plz", "why would you pick nami", etc. The nami jungle then says: "will you please just shut up", followed by "You're all so obnoxious. Everyone goes silent and the game goes on as usual. However, things started to get rough when the nami actually started to gank lanes. Whenever they went in, or failed to get a kill she would start pinging the other people involved and saying "You're so bad", even though they were oom or at low health. Whenever someone pointed this out, the nami would say "you're so annoying, just shut up". This continued UNTIL she eventually left the game for no reason at all. This is a first for me, and I'm still in shock at what happened in the game. I never thought that anyone would actually do something like that.