Stress, so much stress

My mother used to be a heavy smoker, and about five years ago she replaced that bad habit with another. She chews nicotine gum, in very large quantities. I'm telling you this because she has tried to quit several times, and each time she becomes a...Not nice person. She yells at everyone, even our cats. She cries at the drop of a hat, blames us all for her her stresses and difficulties in life, that she says she hates so much. Her modus operandi is she quits for about a week, just enough time to drive us all crazy and send me into a week long anxiety attack, and then she goes back to chewing her gum and she is pleasant as can be. 
I love my mom, I really do, I want her to be happy and it hurts when she is telling us all how much she hates us and her life. I know life hasn't been kind to her (abusive parents, bad first marriage, past brushes with disordered eating) but we all try to make her happy. I know that its my fault she is unhappy, I know I put a lot of stress on my family. I want my mom to love me but when she is like this I feel like she truly despises  me. I mean, I deserve to be treated this way and in a way it makes me feel better because when my family is mad at me it hurts but I know they are justified. 
Its just incredibly stressful and I'm trying very hard to not self harm and to be a good daughter and not cause any problems. I keep trying to tell myself that as long as she's yelling at me she isn't yelling at my dad or my sister, who don't deserve it. I do, I'm the failure and the anchor that is dragging my family down. 
Everything will work itself out I guess...I feel crummy for writing this because I feel like I'm painting my mom as this horrible person and she isn't, I know nicotine withdrawal is hellish, I should know I used to smoke and quit. My mom is usually very nice and always looks out for me. The least I could do to pay her back is let her relieve stress on me.