Why are some girl best friends like this?

In my city, there is a boy who has a girlfriend.

The girlfriend has 7 girl best friends who are all attracted to the boy and all act romantic to the boy especially when it comes to sex. The girlfriend's 7 female best friends are all attracted to the boy romantically and sexually. The girlfriend is okay with all of these.

It's like the boy has 8 girlfriends.

Why are some girl best friends like this?
Why are some girl best friends like this?
Post Opinion