This is the 10419th most frequent Russian word.
ведущей
"Leading" or "host."
In this sentence, 'ведущей' refers to a person who hosts a television show, showing its usage as a noun participating in the instrumental case.
Сегодня к нам пришла ведущей известного телевизионного шоу.
Today, the host of a famous television show visited us.
Here, 'ведущей' is used as an adjective describing 'роли', meaning leading or principal, showing its usage to indicate the primary element.
Она играет ведущей роли в этом фильме.
She plays the leading role in this movie.
In this case, 'ведущей' functions as an adjective describing 'компания', indicating its dominance or leadership in a field.