Kate Middleton’s life changed drastically when she became a part of the royal family.
The outlet reports that William requested that Kate be addressed as “Princess Catherine” upon their marriage.
However, royal protocol prevented that from happening.

This was, though, to reward her for years of loyal service."
However, it seems that Kate was preparing for a name change even before her royal engagement to William.
“It looks like she’s taking it very seriously indeed too.

Ten years later, she is still widely referred to as Kate.