She developed a relationship with a patient, Denny, who had a heart defect which eventually looked set to claim his life. In order to secure him a transplant heart she cut his LVAD wire in a bid to make his condition worse so he would be at the top of the transplant list. However, when Meredith discovered this, he reported Izzie to the Chief, and her mother, Ellis Grey who fired Izzie.
Izzie's relationship with Denny lead to the same incident where she cut her LVAD wire as her real-world counterpart did in "17 Seconds" but Meredith's constant attempts to please her mother and the distanced nature of the interns stopped them from banding together to protect her, as seen in "Losing My Religion". Also, Bailey's timid nature and fear of stepping out of line with Ellis stopped her from approaching Izzie in her time of need and bringing her back to the hospital, as occured in "I Am A Tree"