In Connecticut you can become what is known as "emancipated" at age 16; this would allow your sister-in-law to move out of her mother's house.  However there are certain requirements.  I have provided you a link that more fully explains what emancipation is, who is eligible, how you go about getting emancipated, and a list of resources to help.Here's the link: http://www.211ct.org/InformationLibrary/Documents/Emancipation%20of%20Minors%20fj.asp