Vampires are harvesting blood for their own personal consumption and benefit (survival but w/e).
Cowgirl is harvesting blood for the good of the community outside of her own, not her own sake (directly at least).
I would say Cowgirl can give the surplus, potentially stale/flavorless blood to the vampires.
And if Vampires want fresh blood they should take a page out of the Succubusgirl playbook.