I need some help!!!

I want to start off by saying that I have given my teenage stepdaughter many chances but recently in the last 2 months she has been skipping her online school. Her father is very upset at her and is trying to explain to her that it’s for her benefits not his. Now when he ask her why she is skipping school her answer is “I don’t feel like it”. Last week (she has had already numerous chances) I offered her a deal. For the book she wanted I will buy it for her only on one condition. If she attends class and does all her school work for one week. A week goes by and she tells me that she did all her work and attended school. Idiot me. Well this morning we get an email from her teacher that she only attended her science class once and has not done her school work. She is in the eighth grade!!! I don’t want her to start acting this way already. I seriously don’t know what to do. I am so angry with with because I trusted her and all I ask was for a week! What should I do? She is only 13!