Rimadyl and cephalexin taken together on an empty stomach can cause vomiting all by itself.
I suggest that you wait a couple of hours to give the stomach time to settle. Then feed her a couple of tbsp of boiled chicken and white rice (no bones no skin). You can even blenderize it to make it sit easier on the stomach. Most dogs like it a lot. When that stays down for about 30 minutes, I would then give her the meds if you think that they did not stay down earlier tonight.
I would also be sure and keep her fluids up by giving her some pedialyte or gatorade through the night. Some dogs like to chew on ice chips and this can help to hydrate them.
If the vomiting continues, you can use a little emetrol (children't anti nausea medication) to help.
I hope this helps!
Let me know if you still have questions.
