Hey
I have finished the Vampire Lord questline and have started doing the assignments for the other vampires to earn gear.
I completed the quest where you have to infect Haron in Winterhold and turn her into a vampire, then I got given the quest again.
And now I can't bite her as she is already a vampire.
What do i do? D:

This one has been reported before.
It is indeed buggy.
You may want to see if any modders have fixed it to not repeat on the Steam Workshop, accessable via the steam client.
Otherwise, save before accepting quests from these guys.