My sister in law is a freeloader

My husband(44) and I(43) have been married for 15 years. We moved to another state several years ago, but 3 years ago hubby helped his dad and sister move to the same town as us. Hubby’s sister is now 32 years old. She has never had a full time job, doesn’t drive, and still lives with her dad. My husband and i have tried to help her. We have encouraged her and tried to help her make her own way in life. My father in law is in his 70s and wont be able to continue to take care of her for many more years. There is nothing wrong with her that she cannot do things for herself. My husband has told his sister that he is done trying to help and that when something happens to their dad she isnt living with us and that she will have to figure things out herself. This has not motivated her at all and she has changed nothing. She said she doesnt think she can work full time because she gets too tired. My husband and I have two teenage boys. My kids are my world and they are good boys. My husband and i have agreed that his sister cannot live with us when something happens to his dad. My sister in law has been told this. Part of me feels terrible that she will most likely be homeless. But the fact that she knows this and continues on making no effort makes me think she has made her choice. I hate to see somebody live such a sad life, but I dont feel like there is anything else i can do to help her. She just doesnt want the help. If she were making an effort and just ina bad place it would be different, but things have been like this for years now. She has even told her dad that if he didnt do her laundry for her she just wouldnt go to work. This issue has just become a huge mess in my family and it is very frustrating. Does anyone have any advice on how to help her? Everytime it is brought up now she just ignores everybody and rolls her eyes.