Certainly anecdotal evidence, and I'm inclined to believe the largest user base may still match your description, but personally I feel like you're describing 4chan, not Reddit.
2) You're making a lot of assumptions. I can tell you without asking her that she has an account because she was talking about the subs she likes the most, such as AskReddit and IAmA.
As for commenting and contributing, she -- this specific person -- is extremely introverted (but not tech-savvy -- I know because "family tech support"), so I would be inclined to think not. As for asking her any of those questions, because she is introverted, I don't feel comfortable asking her -- she definitely doesn't want to hear she was being talked about on the internet, even anonymously.
One thought though...I think you have to look at the way she started the discussion "I saw this on AskReddit..." not I saw this on Reddit, or "the internet, this site called Reddit", that sort of thing. She not only expected us (of which I am probably the most tech-savvy and near to the youngest) to understand wtf she was talking about, but to understand she was talking about a subreddit. And I know one person (looking at my mother-in-law) who had no clue, but there were other people probably 5-15 years older than me who did at least a passable job of looking like they understood.
Go compare a reddit technology thread to a youtube comment section. Big difference in writing quality, avg length of post, use of source and data, etc.
You probably outgrew their age demo and realized that smart 18 year olds are still dumbasses.
While I think this is generally a valid point, I also suspect there's quite a bit of When in Rome effect in play. Uninformed r/Technology posters may step their game up to match the consensus style, while informed Youtube users may feel a bit of pressure to dress down.
If you want to build a reddit, you'll never end up with a facebook, that's just reality, the target demo is completely different.