Well the bottom line is that you're an adult and can do whatever you want - who's making you befriend these people and remain their friend?

To my mind, manipulation is when people successfully get what they want. Most people with BPD don't. To that end i wouldn't say that it's a defining characteristic and this has actually been backed up by research. That's not to say people with BPD are incapable of manipulation but from what i've seen - we're not very good at it.

You're also don't state that others in your life have actually been diagnosed - so i'm not sure how helpful we can be. I wonder whether you might garner more responses by reposting in the relationships and communication board.