Great. Thanks for the additional information. I really appreciate it.
So for her size, she really did get quite an overdose, and generally we see things like lethargy, problems with coordination and even vomiting. At higher doses, we can see things like seizures, ataxia (inability to move correctly), vomiting, tremors and lethargy.
Since she ate it 12 hours ago, the absolute best thing to do is to have her seen by a vet. They can do some blood work to make sure that her kidneys/liver are functioning the way they're supposed to, and may want to get her on some IV fluids to flush her system of the medication.
If there is no vet in your area that is open in the evenings, then you can monitor her until tomorrow and then call a vet as soon as they open, just for the blood work to make sure that those organs aren't being affected.
Hopefully we'll find out that we were wrong and she didn't get the pills, but having her seen, just to be on the safe side, is the best option.
I hope this helps.