Twilight had been sent to a parallel world by (an impostor of) Cadance after Twilight had confronted her at the wedding rehearsal. She'll end up having to go through more than one in order to get home.
When Twilight was taken from her original reality, she thought she would never return. Now she has. War is at Equestria's doorstep. Twilight will have to make a choice. When Twilight does, she’ll have a huge task ahead of her.
A thousand years ago, Princess Celestia banished her sister to the moon, that much we know. What wasn’t known, and what Celestia kept secret was that before her banishment, Luna had given birth to a foal; Twilight Andromeda Sparkle.
Twilight's friends are being ridiculous. There is no such thing as real vampires regardless of what the tales say. There is especially no such thing as the Vampire Queen.