Yes, the sister can petition for her sister and sister's family. However the process of getting an immigrant visa/green card on the basis of a sibling of US citizen petition takes about 10-12 years so you will probably not be able to maintain your status the entire time and you absolutely must be in valid status at the time the priority date becomes current in order to be able to immigrate on the basis of that petition. However, if one of you completes your education and gets a job, getting a green card through employment will be significantly faster.
Answered on Oct 07th, 2012 at 2:47 AM