Please tell me what being toxic is.

So i just finished a game, where I had gotten a report warning after, and heres what went down So my Vayne lost lane due to an uncommunicating vel support who constantly went in, and their Graves ended lane 12-1. We tell the Vayne, stop going in with him and let him die, she says "fuck you i'm tilting". As the game progresses she is still tilting, and we win some pretty big fights. So after we win fights we call a baron, and she says "fuck you im not going". We could have easily won, had she not done this. Then I get reported for telling her the right thing to do. Please explain why someone can intentionally throw, but someone that is doing the best and is trying to get the team straight gets reported. Same thing with dunkey.