In the first place, since she's already attached, you shouldn't
even be tacitly wooing her, much less doing it aggressively.
I guess she got the idea that you like her. However, since she's
already attached and has feelings for someone else, she doesn't
want to give you the wrong ideas and is giving you the cold
shoulder.
My advice to you: stop pursuing her, whether it is aggresively or
in a subtle manner.
I can tell you one thing is for sure: you'll end up hurting a lot
of people if you do manage to steal her from her boyfriend.
Yes, that's what you're doing: you're stealing her away from
someone else. You're gonna hurt the guy, you're gonna hurt the girl
when she realises that she hurt someone else, and if you have a
conscience, you're gonna feel hurt knowing that you had hurt other
people.
So be the nice guy and back off from her.
Just appreciate her as a friend; that is something special in
itself.