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You don't need to do anything here. That piece of bone should dissolve just fine in the stomach acid. I would not try to give any oil or speed up the digestion. I would want it to sit in the stomach for a good 2-4 hours getting chemically digested in the acid. That will help it pass through the gut without issues.
Cats will often times eat whole mice and rats. They dissolve the skulls of these animals, so there shouldn't be an issue with this small piece of bone.
I hope this helps, let me know if you have any other questions.
The main thing to watch for is vomiting. If she starts vomiting, then get her in for an exam and x-rays.
You're welcome. Happy to help.