Some people do engage in poaching, which is the act of steaing someone's bf or gf. While the technique may work for some in the short term, I feel that in the long term, it's not the best way to start a relationship. A relationship should be based on openess and trust. The act of poaching is inherently somewhat dishonest and I think will tend to set the tone for the relationship. You might find yourself wondering somewhere down the line that if you were able to steal her away from a commited relationship, maybe some day she'll do the same to you. Even if such thoughts are only fleeting and more subconscious than not, they still tend to affect the backdrop of the relationship and probably more so than you'd think.
My advice would fall in line with what has already been said. Present yourself to her as you are, and let her make her own decisions, and in her own time. Relationships are as much about having the right pepole, as it is about having the right timing.