Allie, I spoke with ATI Carpet and Upholstry Cleaning on Long Island. I'm thinking of having some rugs professionally cleaned in the near future. And while I was calling ATI, I decided to ask them about your situation, too. The lady there said to go to the store and buy a bottle of White Distilled Vinegar and put it in a spray bottle. Using a spray will keep you from over wetting the blood stains and causing further problems. And only use White Distilled Vinegar.
And Lisa said to use a 1/2 and 1/2 mixture of White Distilled Vinegar and Water. And she also said to work in an upward blotting motion. That way you will avoid jamming the blood stains down deeper. She also said that using the Vinegar should help with the smell.
What kind of unpholstry is it? Cloth, Suede or Vinyl?
Good luck with it!
And Allie, I doubt the Car Rental company will make you pay for the car. If they are reputable, they should understand that accidents happen.
I hope you and your friend are feeling better today. Don't worry about the car too much. It's a problem that will pass with time.