Fair enough. It's not that the sentence is awkward or anything (as if I could tell!
). I was just thinking it would've been simpler to say she was a girl whose twin had died at birth,
if that's what happened. 
I
think I have just one more question (but every time I think that, I'm wrong
). Is 宿泊 a room in a hotel and 宿泊先 the person who runs the hotel? Or is 宿泊先 the hotel itself (or even your residence??)? Or is there any practical difference at all? These were used in different sentences and I'm trying to understand the distinction between the two.