Just my 2 cents:
I do think NPD types are sometimes attracted to HPD types, but the deeper dynamics are not so pleasant.
So this is what I learned about myself too -
First, if she is an attractive female with HPD, there are going to be many males who will pursue her. True enough, their motives are not so saintly no matter what they are telling themselves about the whys (i.e., if they were not sexually attracted to her they wouldn't feel or act the same). Because of this truth, many will say or write whatever she wants to hear to gain her favor.
Second, and the real key matter for the NPD type, is this is also a situation that appeals to the NPD types self-esteem issues. Not that she is getting so much attention, but that while NPD types may have a strong wall of 'I don't need others approval', deep down they really do. They end up envious of their HPD counter part on some level, even infuriated that she so easily acquires supply from others, which leads into ...
Third, any kind of 'control' the NPD type thinks he has over her is at best fragile. She may allow it, but it's strictly on her terms and this also drives the NPD type to obsess. The reason is she is NOT interested in have a logical discussion about this or that. She is more driven by others attention and approval. Therefore all she has to do to 'win' and be right, is to find someone else, often of the male sex, to side/agree with her. See point #1 why it's easy for her to do. Others agreement proves she is right, both in her own mind and the proof that others agree. If she can get them to gang up on her NPD partner, even more proof the ball is in her court. The NPD type cannot cope with being 'wrong' let along being ganged up on; he must be right, and so will dig in deeper, trying to figure out some logical argument or scheme to win and repair his damaged self-esteem.
Fourth, the final part of the ugly truth is that often very little of what she does really has any significant effect on the NPD type, *if* he had never gotten involved. Problem is the NPD type did get involved. Again see point #1. That's how it started, except that his overwhelming need to 'win' causes him to become far more obsessed with her than many other 'fan-club' members. Worse still, those not terribly involved members eat at the NPD types ego even more. They can so easily play along with her because they don't care. They are just playing the odds, maybe they'll get what they want (usually sex) or some attention themselves because that's all they want. If they don't get what they want, they just don't care. The NPD type on the other hand has a much deeper stake in the game, and realizes those other members are actually in the stronger position, because they don't care either way what happens next. They have nothing to lose, only potential gains by being agreeable with/to her.
Solution of course is simple

Let her win. Also it's a good opportunity for the NPD type (myself included) to stop, and take some time out to learn something about ourselves. In reality there are probably millions of people with HPD, and none of them are causing us any direct harm, unless ... one gets involved.