This is a matter of self confidence. If you don’t believe you can, then you can’t. That’s the easiest way I can put it. This is something you have to work on. Something that helped me gain confidence in the past was smiling at every girl that I walked past. Didn’t matter if they were good looking or not, I smiled regardless. If they were hot, I’d say what’s up, and often times they would initiate conversation with me. Conversation with every woman, hot or not, is good practice. I actually made a pretty long post about it all here: Help me out! Need some general advice from all you dating guru's out there it’s about halfway down the page.
Pheromone wise, try A314 if you haven’t already. 2-3 drops should be good. All the TUTH and -none in the world won’t do a thing for you if she isn’t attracted to you to begin with.
Then there is most likely nothing you can do about it, she is hard-wired to be self-destructive. Don’t be surprised if you don’t get anywhere with her. She was probably burned very badly in the past and is still getting over it.
Also, are you trying to have a serious relationship with this woman or just play the field and see what happens? If you have your mind set on her then I guess pursue it, but if it’s just something you are curious about, you may want to rethink it. Have you thought about the possibility that she just isn’t into you? Or maybe she doesn’t like younger guys?