It is really unfortunate when our own family does not understand our disease and how it affects us. It sounds as if your sister needs a little education about Lupus. Your big concern should be how your parents feel. Do they understand your Lupus? Are they educated about the disease, its symptoms, the overlap diseases that occur with Lupus, your medications and their side effects and the fact that Lupus changes and is replete with relapse/remission?
Talk to your parents, explain these things to them and ask them how do they feel about you living with them while trying to manage your disease? I would bet money that they, in no way feel like your sister! Giving your sister "The Spoon Theory" is a good start. Invite her to come to this site and read some of the member's posts so that she can understand what you are going through.
No one can tell you what you are and are not capable of doing with this disease! She has no idea if you can work a 40 hour week, she does not have your disease. Only you and your body know what you are able to do. Your sister needs to also learn how stress can aggravate the disease and if she is going to continue to be the cause of your stress, you will have to redefine your relationship with her.
I would also bet that, if she were in a similar situation, she'd be seeking help from your parents also and that you WOULD NOT begrudge her for that!
As long as your parents are understanding and supportive, you should try not to be too concerned about your sister's opinions, especially since they are all based in ignorance about this disease.
In any case, we are always here for you and we truly understand what you are going through. You can always come to us and we will always give you support!
Peace and Blessings
Look For The Good and Praise It!