It depends how advanced that is.  Sometimes it just involves something called a cone biopsy being done where they cut part of the cervix away that is affected.  Other times it may involve the whole removal of the cervix, uterus or ovaries.  As I say it depneds how advanced it is.  Your sister will need a lot of moral support and this type of cancer if early detected has good recovery rates.  It sounds to me like they have caught it early.