virtual stranger
Anyone you have met and got to know on the internet but never in real life. A virtual stranger remains a virtual stranger no matter how well you know them on the internet. You could be sitting there naked 24/7, staring at each other’s personal items on your webcams, but if you haven’t met IRL, then you’re still virtual strangers. 
'So, you've asked SlipperyChick to marry you?'

'Yeah, well, we've been together for three years now. We see each other every day and we cyber constantly.'

'Hmmm. I hate to break it to you, mate, but the internet and real life are NOT the same thing. You're still virtual strangers.'