I'm citizen what happens if i aply for my sister that lives in usa
If she is illegally in USA, nothing will happen, and very likely she will not be able to obtain a green card based on your petition (sibling of a US citizen) because of her unlawful presence and being in USA illegally or out-of-status. You should consult a lawyer before deciding what to do to help her.
www.law-visa-usa.com
It depends on your sister’s status in the U.S. If your sister has been living in the U.S. illegally, I am afraid, she will not be eligible to adjust her status in the U.S. since she will be subject to the (ten or three-year) bar depending on how long she has been unlawfully present in the U.S.