You don't need to destroy him but rather to destroy they connection she has with him. Now, I am no suggesting for you to do this but this is the way. Whenever she mentions the bf just ignore it. In your mind she should be a single girl. Whenever she mentions her bf just space out and when she says " so what do you think" or something like that just reply "what" this will totally get her more attracted to you. Remember girls communicate more with their body language than their mouths so pay attention to her body language. I learned this when I was trying to get a lay with a girl. She was telling me how she wont have sex with me. So I decided to experiment I verbally told her I wont have sex with her but my body kept sexually escalating and feeling her all over. So she said " what in the world are you doing " I told her we're just making out no sex tonight but continued to escalate soon enough I was inside her. So just pay attention to her body language.