Put the following into indirect speech:"I meant to plug in the electric blanket but I plugged in the electric kettle by mistake. I'm always doing silly things like that," she told her guest.

При переводе утвердительных предложений из прямой речи в косвенную мы изменяем времена глаголов в придаточном предложении согласно правилам согласования времен, поэтому:

She told her guest that she had meant to plug in the electric blanket but she had plugged in the electric kettle by mistake and she was always doing silly things like that.