Hi Momrose,
You may want to consult a local attorney who is familiar with your state and local laws and enforcement bureaus. But, you need to be careful about using the word or idea of 'rights' in a workplace situation. Most domestic workers are not generally covered by DOL workplace regulations. Wage and Hour standards may not even apply.
US Dept of Labor is usually the agency blamed for most employee issues and they maintain a very complete website.
http://www.dol.gov/If I am reading your description correctly, my first impression is that you have no 'rights' that are not specifically established by a contract between you and your direct employer. If that is the 'sister-in-law', and you have nothing on paper, it may just be that you've just been fired.
See an attorney!
Good Luck!
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