I Hate People Sometimes...

So I repaired this persons laptop for $35 and now she wants her money back because it won't even turn on... So it appears Windows didn't shut down and was stuck, so instead of per force shutting it down she left it on all day... No, I did not screw up... Windows sometimes gets stuck, it's happened to me a few times as well. Problem is I stayed 3 hours to repair her computer which I showed her every single step I did. So I told her I'll get onto the phone with her and trouble shoot (could be an overheat problem) but she decides to tell me she's going to bed and that's that. I don't want to give the money I earned for her screw up... What do I do... She has all my information pretty much...