I'll go against the grain and say go with one day, and don't feel like settling in is an issue. It's really not that big a deal, one day vs two days. If you're happy to take it gradually, starting with one hour, then three, then maybe more depending how long she lasts, then it is most likely she will settle in.
From my experience, I've found that it's how parents and staff handle the first few weeks that affects how they settle, far more than how many days they are in for.