The meeting of Nicole and Dick on the funicular was heavily symbolic of their relationship. Fitzgerald explicitly tells us that the funicular works by having the descending car pull the ascending car up. I thought that was beautifully done as foreshadowing of the course of Dick's and Nicole's marriage.
I only half agree with you, though, on the nature of their feelings for each other. I do think Nicole drained Dick, but I also think he really loved her--the reason he resisted Rosemary to the extent he did. Both Rosemary and her mother are quite pernicious, by the way. Anything for the experience and damn the cost to others.
Does anyone else think that Rosemary also had an early sexual experience, not incest per se, but that she was pimped out by her mother? And yet she, unlike Nicole, was able to move past it.