Ok, I've devised a master plan which should get you in the clear.
As soon as she gets home from work/college...etc, tell her to sit down and relax, and that you will cook dinner tonight. Ensure she comsumes vast amounts of alcohol over the following hours. Spike her drink if necessary.
Once it starts to get late: "Come on you, let's get you to bed. Look at you, you're a state, you've drank FAR too much again. Oh the things I do for you..."
Place the straigheners on the floor. Assemble them so that they look unbroken. As you're walking her to the bedroom whilst stabilising her, try and guide her into the path of the straighteners so she treads on them:
"Oh look what you've gone and done now, you've broken your GHD hair straighteners. You silly n00b."
If she manages to avoid the straighteners step on them yourself, imply it was her and repeat the above line.