Your sister has come home from being oversees with her hubby and you don't say why she is home and not there anymore.
My friend went to Germany with her hubby, he was a civilian teacher on base at the elementary school. For Christmas he got her and the kids plane tickets home and kicked them out. It took her months to be able to face the world. She had a home here in town that was rented out and as soon as the renters found a new place she was able to move back in her home and start trying to create a new life for herself. They slept on blow up mattresses and bought thrift store clothes, got food stamps, etc...she had no money, no family, nothing. She was barely able to put one foot in front of the other for some time.
It took her nearly a year to get her furniture and personal belongings shipped from Germany, all she brought with her was what she could pack in a suitcase. Your sister has been here 2 weeks and you have already made plans to charge her rent, have her cook, and have her babysit?
I think she should talk to the local military people and find out about housing. She would most likely be happier on her own and able to go about her business as she pleases. If that is not an option then something is going on that you don't know about. You might try and talk to the hubby if you know how. I would have no idea.