Celia

She was about 13 years old at the start of the series

Before Reincarnation of Ye Song
Celia's life in the castle was actually pretty decent; she could get a certain amount of money to spend every month, and had maids to do the housework for her. She was at the same level as the leader of the maids.

Rudin Kingdom Chapters [Ch. 1 - Ch. 35]
Celia and Maggie came decided to come earlier than others to welcome Angele back to the castle so that people would think they were close to Ye Song if they were the first ones to welcome him. It is speculated that their parents asked them to do so. She later had sex with Angele during their journey to flee the war.

Ramsoda College Chapters [Ch. 36 - Ch. 65] Edit
She discovered her talent for music and has begun learning from a teacher.

Angele Rio
She is younger than Angele so she called Angele 'brother' along with Maggie. Angele had a crucial position in the family, so relatives like Celia and Maggie must be careful when dealing with him.

Trivia
Miss Katyusha was the mother of Celia