I'm entirely confused by this. I have my G+ account linked with youtube. Just now I unlinked them, and changed the visible name from one that was obviously mine to a more anonymous name and posted a comment with absolutely no issue.
No picture, no name, no link to me. And this is from after linking the accounts and then unlinking them (which took under a minute to do and was pretty easy to find).
I changed from my real name to somenamefortestingpurposes, and seem to be able to change this to anything else. I've also tested posting comments with this, and they don't appear with my real name.
I also have the option of deleting my "channel" which I think is pretty much the same as deleting my youtube presence.
What works for Youtube is to create another channel and use that channel and the created page to post comments via pseudonym. I can switch between my original Google Account and the newly created channel. I don't have an option for my primary account through. For this does not matter but if you had personal data in your old Youtube account there is no easy way to hide this information without loosing Google+ as far I understood that problem now.
So I guess you also missed the part where her comment showed up on her real name and it surprised her?
(and let me ask in advance not to give me that "she may have accidentally clicked some button on one of those popups and given permission" crap. That's like seeing the vampire's fangs in someone's neck and saying "But you invited him over for dinner!")
I actually have two Google accounts, my "real" one and the one I use to joke around on video game clips on YouTube. When Google strongarmed the second one into g+, I knew that even if I decided I wanted g+ for some reason, I would never, ever, ever want a g+ page on that YouTube account.
So imagine my surprise when I received an email beginning:
"This email was sent to you because you indicated that you'd like to receive Google+ Pages performance suggestions and updates"
Go to Hell, Google. I asked for no such thing, and if you somehow tricked me into accidentally not opting out of any such thing, you can still go to Hell. So if anyone says g+ tricked them into something, I'm going to believe them barring hard evidence to the contrary.
No picture, no name, no link to me. And this is from after linking the accounts and then unlinking them (which took under a minute to do and was pretty easy to find).