Nothing nice about the nativity

There is a rather disturbing story being played out on my sideboard.

Message: "God's Holy Spirit will get you pregnant with his Liberator.'
Mary can hardly believe it - she's a virgin: how's she to have a baby?!? But she hears him out, realizes the privilege and goes for it
Rob Lacey Street Bible

What on earth must have gone through her mind? what on earth was going on?
I'm pretty sure it didn't feel "all is calm and bright".