People who are always needing to borrow money

I have a sister who I'm not very fond of. I've just recently started talking to her again, and ever since she's constantly asking for money. Which is nothing new, she's always done this. However I just find it very rude considering our relationship is rocky, and I personally will never help her. Her and her boyfriend both work and spend there money on stupid stuff all the time. She also receives government assistance and blows through it or for instance uses her food stamps illegally by "trading" them. My husband would be pissed if I ever loaned her money, well more so just gave her money. There is no loaning because you'll never get it back. So today she asked me for money, and I'm at the point where I don't even know what to tell her anymore. What do you say to these type of people?! More so what do you say that gets them to stop asking? I'd honestly like to tell her how I really feel but it's not polite.