It could actually take up to a few weeks or a month for them to bmocee fully adjusted to each other. One way to make the process a little easier might be to switch out their blankets or their favorite bed or pillow. If Shy has a blanket, wrap Gracie up in it or let her sleep on it and give it back to Shy. Maybe do the same thing with Shy for Gracie. Something like this will help them get used to each other's scent. Keep in mind that they may never be best buddies, especially since they are both female. Hopefully they will, but there's always a chance that their personalities may just not mesh well enough for you to find them snuggled up together in the laundry basket together. Yay for adopting a shelter kitty!