Some psychologists - I saw one for a bit - think of BPD as just a way of describing relationship patterns and not a disorder. Though I don't have BPD, I actually like this approach - it seems far less stigmatizing to me than slapping a label on someone (but that's me, I hate labels and diagnoses). The diagnosis is a judgment call - difficult patients tend to get labeled with it, for instance. It also bothers me that women are more often diagnosed with it than men, like 3:1. Something's up there (to me, anyway).

So I'd probably like your psychologist (and I think she is right that you can strip down mental illnesses to a few key symptoms, the ones that can be medicated). I don't think she's dumb, she just has an opinion - but if her approach on this has this kind of effect on you and your relationship with her, yeah, you should probably move on.