I don't think it was some sh!t test, and I don't think it was done out of pure evilness... however that is a possibility. Not every bad outcome is purposeful on anyone's part.
I think she is careless, had some other issue that was in the way, and like I said, careLESS. Without care, to your feelings or time.
This was manslaughter, but not 1st degree murder.
Whatever the case, don't give her a second chance. No matter WHY she did that, she is a straight B!TCH for having you walk over there, then leave you hanging. She could have contacted you somehow. And that is not the part that I thought made you look kind of desperate. It was the part where you didn't care if she was sick, or ditzy (lost the keys). It isn't about what SHE wanted ("are you sure???" u asked her), its about what you were OK with.
Next time a chick is not well, you should act like you'd rather wait to see her when she is better. Or less ditzy. Or... AVAILABLE completely, without EXCUSE or STORY.