I also have not received "The Gift", but reading this thread has given me several options to get past turning that wench in Markarth into a Vampire for a second time...
I have loaded a previous save, but then never turned in the current quest because Vingalmo keeps wanting me to turn the... woman.
So I think I'll wander around and talk to everyone that I
have turned so far, and see if that doesn't work.
I've tried the "kill-the-quest-target" option, but then Vingalmo just shut off and won't say a word to me, and no one else will give me any quests either. They just tell me that Vingalmo should have something for me, so that option isn't working.
Oh well. I guess I'll run around and talk to a bunch of Vamps I've made and see if that works. I'm at the crossroads where I have turned all three people, but Vingalmo won't give me "The Gift" so that I can turn Muiri into a Vamp.
How hot would that be? Alchemist chick that loves me for slaughtering her bandit ex-fling and her ex-BFF, and now she could be a Vampire plus she's just a bit crazy? Hot.

*glares at Vingalmo* Are you essential? Because if you aren't, I'm coming for you...