Thanks for answers.
Aubrey's evolution, I don't know if it's intended or just "lucky" coincidence, have sense.
She have some family induced damage, inferiority, low self esteem, feeling of not being worthy, not being wanted etc. Those kind of types are often "bicycles", because: A - they seek feeling of being wanted, which they get from sex; B - at the same time it serves as "defensive mechanism" not to get "unworthy" again(if being refused for relationship etc), so they do "bang buddy" thing, as "their choice" - you can't dump them or not want them for relationship because "BB is all they want".
When you get closer, earn trust, especially if you stick for her and defend her with family etc, she'll show her true self, what she actually wants. To be worthy, to be "enough" for someone. And she'll reciprocate with same level of loyalty. Therefore "jealous monogamy".