Well, they will be "pseudo twins" but does it really matter if people think they are twins? The names are a bit rhyming but will you use nn? If the nn are different, it does not matter that the formal names sound similar.
You could avoid this by calling her
Caroline,
Carolyn,
Carola,
Cara,
Carys or
Charlotte.
"But it’s all right now.
I learned my lesson well.
You see you can’t please everyone
So you got to please yourself."
Rick Nelson,
Garden Party
"It does not become me to make myself smaller than I am." (
Edith Södergran 1891-1923)