Will a 6year old cat with diabetes survive without insulin?

I don't have the money nor the heart to put my cat through insulin shots if she has diabetes. (I'm 99% sure she does she fits the symptoms. she was really over weigh due to the fact that she hadn't eaten a good meal in a month or two when we first got her. So she gorged and became obese. then she just recently dropped all the weight and is now severly thirsty all the time but still eats.) is there any way my cat will survive if I don't give her insulin? I know money should not matter but I just don't have a hundred dollars a month... I'm already paycheck to paycheck as it is. Or is there any alternatives to the shots? Something cheaper? I can't lose my cat. She's everything to me... Thank you for helping me.