The best thing that you can do to be sure that she at the battery is to take her to your vet to have a radiograph done. That way you can be certain if the battery has been ingested. I've had similar situations, where owners are sure their pet ate a battery, and the radiographs showed that there was nothing in the gastrointestinal tract.
You might get lucky and find she hasn't eaten it.
If she has, then.... that is something that can go down a couple routes. Obviously if it is there, they could try to get her to vomit it out. If it comes out great! If it doesn't then surgery might be considered. This gets the potential problem resolved the fastest and most controlled way. Could a battery that size pass through her intestines? That is something there is no way to give an accurate answer. It all depends on the size, shape of the object and the loops of bowel. I can't say yes it will, or no it won't.
I would encourage you to visit your ER clinic for the radiograph to see if it is there. And then a plan can be formulated as to what to do.
If you can't get in to the ER clinic, you can try to induce vomiting at home (if it comes out great.... if it doesn't... it may still be there). Here is a site that explains it.
If you're going to wait to see if it passes, we don't want to see her getting sick (vomiting), not eating well, becoming painful in her belly, or just getting depressed. Those all could be signs of it not passing. When something gets stuck, it then starts to become a very serious problem that could be life threatening if not dealt with quickly.
Hopefully everything will be good with your little one!