Thats a tough one. That sounds like a situation that will take a little time and proper planning. Pheros will not help you just snatch her away all at once, but they can help turn things around.
If you already know her and feel comfortable initiating conversation with her, then you don’t need Instant Openness, for that anyway, though it would still be helpful for your general shyness.
A314 will give you a higher “social value and respect” aura. Though with someone who is already accustomed to your phero signature, it might take a few exposures for them to understand and accept your new signature. A314 can also make you seem a little intimidating, and, especially if you are using it for a romantic situation, is often best softened with something like Instant Shine or Instant Honesty.
Does she trust you? Can she confide in you? Instant Honesty is excellent to help in that department. For a woman to feel comfortable enough to take things to the next level, or to become involved in a relationship, trust is extremely important.
Which brings me back to Instant Gentleman. You didn’t share much about the guy she is with now, but if he is any kind of an unreliable flake, that is a huge turn-off for most women. As I said earlier, Instant Gentleman will help to heighten her perception of you as a solid guy who can be counted on.
Remember, Rome was not built in a day. This may take a little time, but with proper planning and understanding of her needs, and what needs of hers are not being met by this other guy, you can definitely accomplish this.
Don’t use “sexual” to try to get her back, if you know you guys had good sexual chemistry, that is enough for now. Work on the trust and dependability aspect, don’t even think about the sex part until you are absolutely sure she is ready for it. And that includes waiting until she is sure that she does not want to be with this other guy, and actually leaves him. You don’t want to put her in another “guilt” situation, that will only make things worse. Women tend to be more sensitive and feel more guilty about sex than men do.