How do you repay your sister whos cared for you

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Just a quick back story. My sister is my best friend. Always has been. When we were young are momma was always sick and or was just gone. Ans my daddy was in the military and firefighter never home. But they divorced. And we had NOONE like they both went through midlife crisis together. We at one point had no water, electric, gas or food. Nothingm my sister was 15 years old and worked at a farm to help feed me and my little sister. She has ALWAYS been there for me. Fast forward to now. Im 25 and she is 28. She still does so much for me. If im in crisis financially. She is there. She buys my baby(her niece) SOOOOO much stuff. Even if i tell her she doesnt have too. Anyyime i see her even if its for 1 second. She will look around her car for soemthing to give me. Like she stopped at my job the other day just to say Hi, and gave me Skinny girl coffee flavoring and a granolla bar. I told her how I am trying to get certified for medical billing and coding(i already do this but with no certification). She bought me the exam book and study course. HOW IN GODS NAME CAN I EVER REPAY HER. She has a heart of gold. She is golden. We have had a tough child hood. But we been rock solid together our whole lives. If she ever needs help she could ask me but her and her husband are beyond financially stable. So she never wants anythign or needs help. I do buy her random thigs i know she likes when I see them. I just feel drowned in her kindess. I love her to death. I just wish i could as much for her as she has always done for me.