who made me Jeanette older sister?!

everything was perfect

I had everything in the palm of my hand

a perfect family , a loving adoptive parents and a beautiful cute younger sister

and a busy carrer with been one of the best know idols in my country

but everything had to end just like I got stabbed in my stomach

but when I re_opened my eyes I found myself in this baby body

soon after I found out I got reincarnated into the famous manhwa who made me a princess

but not as the female lead Athanasia , nor Jeanette a side character

but as a non existent character {name} margarita

the older sister of Jeanette margarita

what's going on ?! I am sure Jeanette had no other sister . especially a big one?!

but with time progress my big sister insects are awaking

".big sister ! let's visit the green house!."

".big sis read me this book please!."

".big sister is so pretty!."

gosh my sister is so cute !!

well weaponed by the knowledge of the future I will work hard to unsure me and my sister a happy free and calm life

I will help her dodge all the red flags and protect her from getting used over and over again from "our family" and dodge all the drama of the imperial duo
-cough- trio

but why is everyone suddenly interested in me ?

ijekiel:".when I grow up I will marry you milady !."

Athanasia:".I chose you to be my playmate."

Anastacius:".you have strong mana how about I teach you some tricks ..? ."

Roger :". you're majesty may I present you {name} you're first born from your late finance!."

WAIT WHAT ?!?!