This picture of "affection" also has hints of sinister sensuality: Amanda is somewhat trusting and at ease. Rachel has a subdued, predatory expression and is in a good position to get Amanda in an unpleasant hold. The friction is the drive of their mutual, sexual attraction to each other.
Thanks. I really spent so long morphing their faces and testing out expressions on them. The best-designed characters naturally fit the dominant expressions of their personality. So what their face looks like 'in neutral' gets you half way to the expressions they use the most. Amanda does warmth, innocence and happiness very well. Rachel has one hell of a smirk and a pout.
Nothing so vicious from Rachel. She's not a baddie. She's just another hot girl with some overlapping ambitions. Your perception of her as good or bad will depend initially on how you feel about Amanda.
I think placing them together like this really pinpoints their differences - not that it was really in question before, but all artists tend to have a bit of overlap stylistically (I dare you to tell one anime character apart from another if you take their hair off ; P ) so to see how distinct they are in this tasteful piece really helps one appreciate them both! : D