Good question! She's not a vampire. Vampires are not real.
Getting more into the specifics, though: She's only 28 years old. If you drink a lot of water and maybe get some good skincare products, it usually doesn't take a whole lot to not age much while you're still in your 20s.
Will Prince Harry Take the Throne?
Considering that Harry's fourth in line for the throne, and the third in line for the throne is still an infant, it would take a series of extremely unfortunate events for Harry to inherit the throne. But he's more likely to become the King of England than, say, Justin Bieber.
Fifty Shades of Grey started out as Twilight fan fiction before turning into its own fictional kinkfest, so it's not real on its own.
There are people who live their lives similar to Christian and Anastasia, though, with a few realistic modifications. If you want to read more about real life dom/sub relationships, The Atlantic Wire interviewed a submissive woman who wrote a memoir on being a sub, and The Stir interviewed a dominant man and sex educator.