There’s a typical setup where the love interest comes across the vampire in situation where it looks like he killed someone; this is often the obstacle that has to be overcome in the third act of a story. But the cashier is much smarter than that. She knows the vampire well enough to trust him and doesn’t freak out. She brings her esoteric knowledge to bear as a sort of amateur Macgiver-esque EMT.
It is low budget and largely unavailable. I watched it in 10 minute chunks on YouTube, and it is apparently also available with commercials on some random Roku channels. It’s a very fun movie that does a lot with a little. Seek it out!