A petition by your LPR mother for your unmarried sister will generally be faster than one filed by you. While your mother's petition is in F2B category.[Adult unmarried daughter of LPR], your petition for your sister is in F4 category [sister of a US citizen]. By way of comparison, the petitions which are now current under F2B were filed Nov. 2005 (about 8 yrs ago, while petitions filed under F4 that are now current were filed May 2001 about 12 years ago. Both petitions take comparatively lengthy wait times, [8-12 yrs] it is still possible for your sister to come to the US within an even shorter time frame. This requires consultation with an experienced immigration lawyer who can fashion creatively shorter means for your sister's entry into the US.
Answered on Jun 09th, 2013 at 10:12 PM