Actually it depends, you know this our heart can deceive us so much. You might be thinking that your friend actually want you guys together, not knowing that he is jealous, he has to play along with you. But you mistakenly fall off ,he fall in. One thing we should have in mind is this

what is not yours is not yours no matter what and there is nothing you can do about it.

every body isn't thesame. For me if you don't treat her right, I will.

Every body deserve the right to be loved and to love.