Hello, I'm Dr. Deb.
I recently came online and see that your question about Mia hasn't been answered. I'm so sorry that you've had to wait for a response, but if you still need assistance, I'd like to help if I can.
It certainly sounds as if Mia may have ingested your medication. Signs could be seen for a dog this size at about 60 mgs so if she ingested 150 mg, she would show symptoms. The most commonly seen signs include: balance issues (she's acting like a drunk sailor), weakness, tachycardia (increased heart rate), agitation (or just the opposite, lethargy), vomiting, diarrhea, panting, hypotension, and/or tremors....and can last 24-36 hours.
If she's only experiencing balance issues and no other symptoms, then you can continue to monitor her; she should be fine after another day or so. However, if other signs should develop, then a vet visit may be prudent.
I hope this helps although again, my profuse apologies for the delayed response, under the circumstances. Deb