Don't give castor oil unless directed by your vet - it will be very hash on her system and may cause more pain and distress, especially if too much is given. A tablespoon of Milk of Magnesia may be given if she is drinking well.
Keep her drinking, have fresh water always available next to her. Using an oral syringe to give her water may be helpful. If she's on a canned diet, add water to make a slurry or add warm water to a dry diet to moisten it up.
Walk her slowly and gently, you may want to have a ramp placed over stairs. Prevent her from needing to perform sudden moves or from jumping around. Even without any internal organ damage, she's going to be very sore from the body bruising, and will take time to heal.
Be sure to give all prescribed meds as directed, keep your vet updated on her progress and report any adverse problems.
And of course, keep us updated on her progress :)
Gook luck with her.