My sister is 21 and she lived with me throughout the whole 2016 year. She did not work - she is an immigrant without an authorization for work. She is waiting to get approved from USCIS for a work permit (she is a refugee). Can I claim her as a dependent?

According to the IRS, "You generally can’t claim a person as a dependent unless that person is a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico. However, there is an exception for certain adopted children."  Unless your sister can meet this requirement, you cannot claim her as a dependent.