I have PD-NOS, but I have all of the symptoms of HPD. I've noticed that I act completely different alone than how I am around or even thinking of others. My therapist agreed when I said I'm basically an emotionally immature chameleon.
Alone, or with family(whom I'm comfortable with).. I basically act normal? I'm kind of cold, sarcastic, and don't value superficial feelings. Around others, though, I turn into this fixated "in love" schoolgirl that's meant to please them and only them. I treat acquaintances like familiar lovers. Best friends like soulmates. And I genuinely DO see them that way. It's like I switch from seeing the world as bleak and rainy alone, then I see it as roses and champagne with a new person. So I act that way. I definitely fall in love a little with each person I meet. (But when they start to love me back, my heart sinks and I run away. Because I don't deserve to be happy? Because I'm scared of finally committing to anyone? Because they only liked the side I showed them? Hm.) I act very dramatic, flirty, silly, caring, and supportive. It comes naturally to me, but it's so different from how I act "comfortably."
It's like I try to be their dream person, since I know if I acted without this defense mechanism they would abandon me. Maybe that's it. I don't know. Do you act any differently alone (or with people you feel comfortable/safe with) and around others?
(Sorry this is so long and sorry if some parts don't make sense-- I added some things in after venting it all out.)