She's just imagining a day when we all run our lives on Facebook. Sorry you dumb bitch but I won't be following you into a world run by Facebook.
Furthermore, even as a teen, I always considered email very much the official way of communicating online. I never use it to keep in touch with friends. I have GTalk, MSN, Skype, AIM, texting and phone calls for that (no Facebook chat for me, no Facebook messaging).
Even now, in my early 20s, I still consider email a way to subscribe to websites, to get my account, to define my identity, and to be a common way to log in to most modern websites (Beats OpenID/FB Connect to me)
I'll continue using email for a way to interact with more official people/bodies than myself. I'd never use it to communicate with someone on in my social arena though.