Friend, the ingestion of a battery brings two concern:
1- The acid causing damage to the gastrointestinal and if they vomit inhaling the acid into the lungs.
2- The possibility of an obstruction by the battery.
This is what you can do:
1- Do Not make her vomit.
2- Give her some milk; the milk will dilute the acid and hopefully prevent any damage to the wall of the gastrointestinal tract
3- Change her diet for the next 2-3 days to rice (75%) and boiled boneless chicken or ground beef. The idea is for the rice to help pass the battery in the feces. Make sure you check her feces; if she does not pass the battery in the next 48 hours I would have her checked by your vet for x-rays.
4- If during the next few days you see the following symptoms: lethargy, anorexia, vomiting, constipated or diarrhea, etc. follow up immediately with a veterinarian. These are all signs of a possible obstruction of the intestinal tract. In the meantime, observe her and change her diet as above then wean her back into her regular diet.
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