Do I have a bad mother for leaving us?

When my dad died last year from a heart attack, my mom just left us. me and my sister where left alone in the house for a year. Mom gave us all her money to pay for bills and food, and she just left us and flew to Utah to her sisters. for a YEAR, my sister was my mom, she took care of me and everything. thank god she took classes in health and carrier education and family care. we both got jobs, I had to lie and say I was 16 when I was 14 (i am turning 15 this year) to work as a grocery bagger in the winter and a carnival worker in the summer, my sister went full time as a worker at whole foods restocking shelves and being a cashier, she missed a whole year of school but her teacher came over on weekends for free and tutored her. We survived, and brought in enough income to stay in the house. My sisters boyfriend Aaron came over and stayed with us every two weeks, he even put in some of his money. Do I have a bad mom? She does freak out at us a lot since my dad died....I'm not sure. She does have a boyfriend, shes happy around him but when hes gone she cries and sulks. Half the time Liz (my sister) makes dinner and drives me to the mall and buys me things. I talked to a school counsiller but she said my mom will get over it...that was 6 months ago. what do I do?Do I have a bad mom?