I am finally attempting to complete the horn of jurgen the windcaller task, but when I arrive at the inn to meet the person I am attacked. I leave and roam for a while then head back, but she still attacks me. I killed one person on my way there. On some path NW and down the mountain from high Hrothgar. Then some imperials attacked me on my way to meet the person but I just fled. Any suggestions?
If you have a bounty, then you have your answer. Almost everybody attacks you with a high bounty, like murder gets you higher bounties. So your kill chain might of ruined your reputation. So just pay of your bounty or any other sayings to get out of your bounty.
Ways to fix solution:
Delphine might have attacked you because of a bounty. Check your bounties in your stats to see your bounties, then go to a guard and pay the fine.
Use spells to calm Delphine down such as Harmony and Calm. This will let her stop combat, but only for a limited time! If the effect wears out, and you're still in conversation with her, she won't start combat.
Vampirism has 4 stages. In the fourth one, NPCs will become hostile to you. Cure the vampirism to continue the quest.
I know you said you did this, but try waiting a bit longer and this will reset NPC's als.
If none of them worked, then you're doomed.