Before we get to Amelia, let's back up a second and talk about what's actually going on in this game. Everything that happens in Bloodborne is arguably the fault of the Healing Church, the whole existence of which is inarguably the fault of a guy named Laurence.

Laurence was one of several scholars who began experimenting with mysterious blood samples retrieved from the "Tombs of the Gods," or what the players know as Chalice Dungeons. Laurence's fellow academics deemed this "Old Blood" too dangerous for further experimentation, but Laurence saw that it could cure any injury or sickness, and eventually established the Healing Church to distribute this revolutionary medical treatment to the masses. We don't get all the details of the timeline, so we don't really know how quickly everything went to hell, exactly; a common theory is that the side effects may have been more manageable in moderation, but that the blood had an addicting quality, or its benefits didn't last without repeated dosage. By the time you begin the game, however, there happen to be major cosmic forces encroaching ever further into your world, and it may very well be that blood users didn't start sprouting hair and fangs until the veil of reality began to thin...or maybe it was the use of the blood that caught the attention of these cosmic forces? We'll unravel a few more of the clues later, but the important thing is that by the time people were turning into doggies, many church members of the church rightfully recognized that this was just plain sick as hell, and their mission went from healing the sick to just improving humanity altogether.

This does not appear to have been the case for poor Amelia, one of the last church vicars still in Yharnam by the time of the hunter's arrival. You'll first encounter her praying before an altar in one of the church temples, an altar where you'll find the decrepit skull of a beast. She clutches a golden pendant believed to ward off evil, and the prayer she actually recites is:

""Our thirst for blood satiates us, soothes our fears. Seek the old blood, but beware the frailty of men. Their wills are weak, minds young.
The foul beasts will dangle nectar and lure the meek into the depths. Remain wary of the frailty of men. Their wills are weak, minds young. Were it not for fear, death would go unlamented.
Seek the old blood. Let us pray, let us wish to partake in communion. Let us partake in communion and feast upon the old blood.""

From this alone, we can gather that Amelia truly believed in the church's original cause. She was a healer, someone who thought she was a part of something good, and she had seemingly been taught to view the blood's monstrous side effects as a product of spiritual impurity; something the truly faithful, like herself, shouldn't worry themselves over no matter how much of the blood they guzzle. I guess it's like people who confidently believe that you can only develop an addiction to something if you're weak-minded or lazy or otherwise morally imperfect.

Well, it doesn't work that way. Not for nicotine, not for alcohol, not for gambling or playstation 4 games and most certainly not for weird magic blood you found by robbing some kind of monster's grave. Maybe she was able to stave off the transformation through exceptional willpower, but it all catches up to her so suddenly that she skips all intermediate hair growth and just kind of explodes into a perfect, fully formed beast. Healthier and more vibrant looking than probably any other beast in the game, but only relatively.

She's wolf-like, kind of, though like many beasts she has a more reptilian sort of jaw structure, with mostly identical sharp teeth in a straight, pointed muzzle with a distressingly wide mouth for a mammal. She also has the stretched out proportions typical of beasts, with big massive Digimon arms and hands. She also has a whole lot of very long, straight, icy white hair, which gives her a truly unique look among any of the game's beasts, along with the signature bandages completely hiding her eyes. She's a tough battle, because she's not only a deadly beast, but one that can keep healing itself.

Bloodborne's tumblr tags also indicate that this is the fandom's single biggest crush, and that she even has fans completely impartial to anything else about Bloodborne; especially among those who are just that into werewolves or wolfy characters in general, but I'm sorry to tell you (or happy to tell you, depending on how you receive this suggestion) that your werewaifu doesn't look nearly as much like a wolf, to me, as she does an opossum:

That's not to say I believe Amelia's beast design was actually based on an opossum, mind you, that might just be a happy accident or my own propensity to see opossums where there may or may not be any opossums, but that leads us to the important point that Bloodborne's beasts really don't allude to one particular kind of animal. They have a lot of canine influence, but they can also have horns or antlers, some retain mostly primate facial structure and we'll eventually be checking out a beast that's at least partially equine. More than anything else, their external features seem to be a chimeric mashup of the mammals people in Yharnam may have been most closely exposed to.

Once you've defeated Amelia, you can touch that weird skull on the altar to progress the game world into nightfall. Whose skull is it? Laurence, of course! You can even fight him in the Old Hunters DLC, where he appears as a beast with some similarities to Amelia, except that he's constantly on fire. So dramatic.

As for Amelia's healing pendant, it's actually a locket allegedly containing a single phrase, pre-dating the church, in fact the mantra of Laurence's rival scholars: "Fear the Old Blood."