Maybe something like "In spite of many difficult life obstacles the past two years, I have found inner strength that I never imagined I had. Since my experiences of the past two years were of the medical variety and involved people I hold dearest to me, I can say unequivocally (sp?) that I want to become a nurse. I want to be able to be there for patients just as some nurses have been there for me in the past. The technical aspects of nursing appeal to me just as much as the emotional aspects. I find the medical field and the human body fascinating and I know that a career in health care would give me a great feeling of fulfillment and a true sense of purpose."
I wouldn't outwardly acknowledge your GPA at all, but if they read an essay like the one above, they are hopefully going to infer that the reason for your gpa is because of a "difficult past 2 years".