An Extra In The Family Is The First To Be Abandoned

I am the youngest princess yet I was discarded by my own family in the Imperial Palace at the age of ten. The Imperial family then lost their power and was caught in the flames of rebellion, and I was the first to be abandoned. Alone, cold and hungry, I lived on the streets until a kind couple took me in and I became Ethel, a commoner. Stella the princess was no more.

Now, after 10 years, I have to return to the Imperial palace where I was abandoned, because my "family" wanted to see me.
'I need a replacement," my sister, the first princess, told me.
“You'll replace my missing sister.” Of course, they don't even recognize that I am the real missing sister, since they never looked at me anyway.
“That’s a tempting offer, but I don’t want it, princess.”
“Are you sure you want to turn down my offer?” Her threat is so clear, but I might as well have my revenge and return the palace to play the role of my own substitute. I will humiliate these people who don’t recognize me, I will never forgive them. They'll try to win the heart of their princess who has awakened her powers, but this time I'll be the one to abandon them.“In the end, I’ll be happy”
The splendid return of the abandoned princess.