I guessed from the start when they revealed what the goal is. That it will end with the limbless girl giving up on it and they continue to live in this arrangement. It's kind of an annoying cliche I see a lot. Where something that someone has wanted and sought after for so long, finally gets it, they in the end decide against it. Could they not of used the mother's heart and limbs? I'm sorry, but this actually kind of annoys me that she never even got the one goal she had. It's not even explained as to why they can't use anything from the mother. Also, working in the black market and you struggle to find body parts? I feel this isn't right.
I really liked the story, but it's just so annoying it went with this path. The story isn't saying it's completed. So maybe something else might happen.
Edit: I'd also like to mention that the absurdity of the surgery. I could suspend my suspension of disbelief. But they are just constantly switching these limbs and heart back and forth. There is no way this isn't good for the limbs. I do think a sad/tragic ending might've fit this better, to be honest. Hell, I was expecting a twist at the end, where the mother wakes up, only to find that the limbs are missing. Maybe her tongue is too. But has been left at a hospital or on a street where someone found her. So she has to spend the rest of her days without her limbs and never able to say anything about what happened. You know, a horror twist. That or the daughter keeps the mother as some type of pet. Though I find that less likely.