Unknown Territory

She is my best friend
He is her boyfriend
I shouldn't want him that way 
Yet I do
Badly
And he has admitted that he wants me
I long for his hand in mine
And we have now entered a dangerous terrain
Unknown territory to both of us
She knows of our feelings for each other
But she knows not of how we act on them
I wish I could tell her
But by doing so I would betray both of them 
I do not wish to hurt her
Yet I do not think I can control my feelings for him much longer
Sometimes passion is your undoing
And I'm scared that it shall be mine