There are actually 2 witches, not one. And they are invisible, so you need to run around and search for them. Don't spent your time for other beasts - Witch of Hemwick will summon more for you. This is not a very difficult mission when you know what to do :)
Good luck and Have a nice game!
Bloodborne The Witch of Hemwick fight. Bloodborne The Witch of Hemwick fight tips.
I am Alex68, my channel gaming and fun alex68acmp: http://goo.gl/zCIqIL