How can I win the heart of a lady I know has a mate, but whom I think is perfection incarnate?

We are co-workers, in a reasonably high-profile government facility. I expressed an interest in her. We exchanged some e-correspondence, and then I asked her out. She readily agreed, but over that weekend she expressed doubts because of trying to do the right thing by her boyfriend. I respect that, and if this were anyone else that would be the end of it. But I am so impressed by her intelligence, her personality and her gentle, confident manner that I can't let go so easily. I have never met anyone like her before where I've been so taken by more than just her physical attributes. What if she's THE one? (Coincidentally, she is also drop-dead gorgeous, but I genuinely see much more in her than just that.) Pretty much a lifelong first for me. I've made a life out of chasing one enticing rear-end or another, sometimes with disasterous outcomes further on down the line.So, is there an answer, or is the answer to just let it go? Somehow I feel I would never forgive myself if I didn't try..