OK Scenario time
So you start dating a guy. You really really like him. He likes you. This may be a great match. So you both decide you want to make it official. But his best friend is a girl. And not just any girl. A girl that he has been involved with sexually. Can you accept their friendship? Do you think it's fair to ask him to end his friendship with her because you are uncomfortable. The girl even wants to meet you and be friends with you since you are her best friend's girlfriend. Could you do this? Is it fair to ask someone to stop being friends with someone if they've assured you there is nothing to worry about?
This was an "ASK THE BLOG!" conclusion to a debate.
Appaaaarently you all happen to be the voice of reason.