Good friends or not?

My girlfriend has a friend (also girl) since many years, they are veeery good and intim friends. They speak about everything.

This friend, knowing that she has a boyfriend (me), is trying to convince her to know her brother, showing her his pictures and always repeating it.

My girlfriend says that she is just jocking... can be jocking, but this story is going on already some months...

I would like to know what do you think about this situation... is she a real good friend or she thinks that that girl is a good friend but it isn't because good friends knowing that you have a good boyfriend don't try to introduce you to somebody else?

Do you understand my point? I am thinking about bad influence...