I hear what you're saying, and I appreciate that you put the time in to write that out, but honestly I'm hearing this kind of argument from so many quarters ("we never look up!" "we all talk, but we never
converse!" etc etc) recently that it's starting to get obnoxious.
Conversation is not dead. People have been moaning about how we're all becoming socially isolated since the publication of the first novel. The art of socialising has been declared dying ever since the first VHS was available to buy and watch at home.
Point is, it's bullshit. People still hang out (in person, not in "hangouts"). Yeah, people have mobile phones, and sometimes when hanging out as part of a group we check them, but it's not like it kills all conversation dead. A group of three people all looking at their phones is the exception, not the rule - it's not like that's what we plan to do when we arrange to spend time together.
As for your lady friend, like you said, that's her habit to break. But you can't assume everyone who hasn't taken a vow not to use a smartphone is the same - I have a smartphone, so do all my friends, and yet we're all somehow able to communicate to one another in person. When I go out and about in town I don't see crowds of people standing around looking at their phones. I see groups of people socialising and talking - if someone is by themselves then their phone can provide some distraction/semblance of "company".
There's also a tendency for us techy types to get caught in our own little bubble - I get my news from HN Reddit and Twitter, so my view on how people use these services is clouded. It's like when a journalist starts using Twitter and writes about how "everybody is obsessed with tweeting, you can only send short messages, therefore the art of meaningful conversation is dead". They don't realise that the "everybody" they're talking about is only those people in their immediate social circle.
I've kind of gone off subject, but my main point is this: Black Mirror isn't a documentary. It's so easy to project your own worst nightmares onto new technology. It doesn't necessarily make them a reality.