Ah, anthropomorphic personifications, always fun. Particularly seeing different authors' takes on Death.
I enjoyed meeting Death and Red Death (was waiting for the other Death to creep around, but I didn't see him...). I liked the bargain for a promise, very devious to pull that kind of bargain in a time of desperation.
But, I found the protagonist to be a self-entitled whinerbaby. She knew the bargain she was making at the beginning, but when Death comes to collect, she whines and complains her way out of it as if she deserved it somehow. Sweetheart, you extended your Grandma's life by 7 years by making your bargain, and then you back out when it's time to collect? How would you have felt if Death had made a bargain and you had fulfilled your end but then he'd backed out of his? I was honestly rooting for Death to either force the bargain or to collect with interest, perhaps by killing her immediately, or by cursing her so that she would kill anyone she touched, or maybe by making her live in the underworld until the time of her planned death. My jaw dropped when he allowed her to talk him into spending just one day with him instead of marrying him. Like, dude, you had a cushy bargain going that she agreed to and you're backing down? That's like trading your Lamborghini for a Razor scooter. It says something for the story that I was rooting FOR Death.