What to do if you just cannot afford private student loan payments?

My sister has private student loan payments that are over $350 a month, from Sallie Mae. Her forbearances are up, so she cannot postpone paying them any longer. The payments are the lowest they will get, they will not lower the monthly amount at all. My sister is single, and makes a very low wage, about $1000 a month. She works full time but makes very little. She can hardly afford her rent, food, car gas, let alone a $350 loan payment. Isn't there some sort of income based payment plan for private loans? There is no way she will be able to pay this amount, so I don't understand why they will even bother trying to make her. It is like asking her to produce something she doesn't have out of thin air. What are her options, besides consolidating (which no one is willing to do right now and wouldn't lower the payment by much) or defaulting?