I'm a total noob when it comes to composite charts and horary charts, so what little insight I can give you will be from a natal perspective.
Some things I'd like to point out:
1. She has a challenging Mars-Pluto aspect. I believe these two energies can be especially difficult to handle for a female. This aspect may very well form an important part of her personality and conscious / sub-conscious desires, especially if Mars and Pluto are conjunct quite tightly. Mars represents a combative energy, one that's all about action. Combine that with Pluto, a planet that symbolizes death and regeneration, power, control, and manipulation. That aspect, if not wielded properly or if there aren't mitigating factors in the chart, could lead to potentially explosive situations and a general lust for power and control even if it comes ruthlessly. Pluto is about complete transformation, a physical / mental / spiritual demolition where the old is left behind and new patterns, new morals are forged. Combine that with Mars, the planet of drive and action, and you could potentially be dealing with someone who'll want to "get ahead" at almost any cost.
2. I'm also a Cancer sun and the key to understanding water signs is that fundamentally we're driven by our feelings and emotions. Cancer needs to feel emotionally and physically secure. As another poster has already mentioned, your relationship with her has a highly sexual bond, but you should probably try to see whether she has emotional needs that are unmet. If a water sign such as Cancer does not feel emotionally secure, they may be tempted to look elsewhere for that feeling, and they might confuse looking for a kind of feeling with a person rather than wanting to be with the person for who he / she actually is. I'm not much older than you and I've been through what I'm describing. It's not easy.
3. Are her Venus and Mars close enough to be in opposition to each other? If they are, she might be someone who confuses love with sex and blurs the two. The kind of person she's sexually attracted to, and the kind of person she might fall in love with may be different, but sometimes she can't distinguish between the two.
4. Pisces moon is very watery, emotional, sensitive, and it has lots of love to give. It's a mutable sign, and if the moon forms hard aspects there might be the sense of drowning in one's feelings and unable to have any kind of emotional clarity. As a Cancer I feel this as well, but I'd argue Pisces has a "broader" kind of love than Cancer.
5. I'd look for aspects, especially hard aspects between her natal planets and the 3 outer planets (Uranus, Neptune, Pluto). One has already been pointed out for you. Uranus is about the need for excitement, freedom, and space. Neptune is about fantasy and delusion. Pluto is about sex, manipulation, transformation, and power. Of course, I'd also look at hard aspects between her personal planets.
6. Does she have any Saturn aspects to her natal planets? Regardless of whether the aspect's a flowing or a challenging one, I feel that Saturn adds a degree of restraint.
EDIT: I just checked your original post. She was born on June 9th, which would make her a Gemini, not a Cancer.