Someone help me.

In the last game I played, I got a person who, in champ select, said that they were going to feed. I am in my promos right now, B1 into SIlver, and I cant dodge or else I completely lose on my promos, and I have been working damn hard to get past this. I am forced to take a chance. In the game, we were doing really well, our bot was killing it, i was doing well in the jungle, so was our top. This mid guy who said he was going to feed stayed true to his promise though and fed diana, so we ended up losing because a fed diana is impossible to deal with. We were winning the game, and this anivia couldnt get over herself to just play. I do not think it is fair that I have a loss because of a feeder and toxic player. She was reported, hopefully she gets banned, but that still doesnt fix the whole situation. I've seen a game be forgiven before, so how can I get this game forgiven?