Im in love,with my bestfriends,little sister what should I do?

Ive known her for almost her entire life now she is everything I want,in a woman shes perfect.i ask because I want to tell her,how,i feel but idk if she feels the same. we are bestfriends and I do everything with her. She is my rock, my heart, and, my life. When she isnt around all I think,about is her. What should I do?????? Our,age differs 5years apart but I forsee no problem being so the fact u dont choose who u fall in love with and things happen for a reason. Should I talk to her? Idk im scared she,may not love me as I love her or she only sees me as a brother figure my only goal is to do whatever it takes to make her happy . Im afraid of rejection because I watched her grow over the years and its starting to pick at me,each,and eveyday. If she didnt feel the same idk how it,would affect our relationship. She is,much more than just another girl I feel as if I cannot be,without her. Please help my heart doesnt, want anythong else.