First, you may petition your sister. But you need to wait for a visa number is available for the category of the petition before she can go to the next step (Adjustment of Status in the US or Consular Processing out of the US). The wait in the F4 (sibling of US citizen) category is 12+ years (longer for people born in Mexico or the Philippines). She would only be able to "adjust status" if she is in the US and in legal status at the time a visa number is available, i.e. 12+ years after you file your petition. Her current B2 status lasts no longer than 6 months, so obviously she cannot do it on this trip. Plus, she cannot enter with a visitor visa or most kinds of nonimmigrant visas (except H and L work visas) with the preconceived intent to adjust status while in the US, so she cannot simply wait until it is close to the time the visa number is available and then enter and adjust either. She would have to go through Consular Processing in her home country.