Nothing, except love, kindness, and encouragement. If you want to loan or give her money to help her out, that's your choice. But it's not an obligation. You're her sister, not her bank.
Few things feel worse than being treated like a cash register by your own kinfolk; yet if you learn that a close sibling has a serious, unexpected financial emergency—not rent, gas, or cigarette money—you should help if you can afford it. Then think about long-term solutions: Offer to help her work out a budget or get credit counseling.
—Anita L. Allen