Oh, yeah, I remember that lady, it was weird. I was a mage and I pulled away from it. I wonder what would've happened if I fell for it? I really gotta do a third playthrough...
But yeah, doesn't Orsino refer to Quentin as a blood mage? So even if Quentin wasn't using blood magic on Leandra, Hawke still has a reason to hate blood mages, because his mom was killed by a blood mage. In fact, this is stated multiple times in the game iirc, nobody ever says "Hawke's mom was killed by a necromancer". Going by what we know, it is apparently necromancy Quentin uses, because blood magic is normally used on people who are still living, and necromancy in real life, refers to communication with the dead, and Leandra was already dead by the time Hawke reaches her, since, you know, her head is on someone else's body...
With the new Necromancy tree in DAI, I was quite confused. I was like 'isn't that blood magic?' and the trainer went on to "explain" it to me, but I still didn't understand. It just sounded like blood magic to me, but as though Bio twisted it around to something else so players could get something similar to blood magic, without the Inquisitor actually being a blood mage (because it would be bad for rep if the Inquis was a blood mage).