Hello. I'm Dr. Berry. Thanks for your question. Mushrooms can be deadly poisonous. It depends on which species of mushrooms are in your yard. Only an expert can tell the difference between mushroom species. They can cause severe liver disease and neurologic disorders.
If you think your dog may have ingested any of these you need to induce vomiting and seek veterinary care. Keep any mushrooms that grow up in your yard remove them.
How would I induce vomiting?
and are there any symptoms that would suggest that she actually ate any? I have no external signs
There may be vomiting and diarrhea. To induce vomiting you can give a couple of tablespoons of hydrogen peroxide.