I showed your site to my sister (who also has tendencies more than your average person as well), and we both agree that our grandmother was/is definitely a sociopath. It's interesting to see her now, since just recently she was put into an assisted living home. She's in the early stages of dementia, but sometimes when something isn't going her way, I see her mask drop from her face and it takes her just a tad bit longer than usual to recover it. I was tempted over the holidays to whisper something to her about it when her mask fell away, but decided against it.
I'm sure she has no idea we know her true nature. I'm not even sure she's self-aware enough that she would even know the label (which I think labels are stupid anyway).
She was definitely high-functioning because as far as I know she was never a criminal. Though I do think there are family secrets about tax evasion.
A side note though, I recently discovered through a scrapbook of newspaper clippings that she had had a hit out on her in the 80s. Apparently, that was an open family secret and I asked her about it (this was before the dementia) and she didn't have much to say about it. I'd even say she was very nonchalant about it. I'm pretty sure most people wouldn't keep a scrapbook about someone trying to have them killed and when asked about be so blase about it. I have so many stories from my childhood that point to her sociopathy it's not even funny. So yeah, the genetic component is there.