If shes 18 and has finished highschool then i feel like its not your problem. She chose to move out here with you, she should have thought about it harder i guess. Ask her why she was so gung-ho to move out to WI in the first place? Is there something that hasnt hapoened since you got there that she was expecting to happen...? I know shes your sister but screw the whole "being lazy, sleeping all day, and not doing anything" attitude. You need to give her a kick in the butt and make her start sleeping at the normal hours and start looking for a job. Or at the very least help out around the house. Shes 18 and youre not her mother, she should be doing something to help out. If she doesnt want to get a job to pay for a flight back to NH then tell her she has to help out around the house for awhile until you can afford to fly her back.

I apologize if i come off as harsh but i have a pretty harsh and negative opinion of lazy people...