HelloCustomer Dr. Hurst here.
Yes, coffee grounds are toxic to dogs. Whether or not they affect her will of course depend on how much she ate. If you believe she ate more than just a tiny bit, expect to see symptoms.
If this occurred within the past 2 hours it would be wise to get her to vomit to help decrease the amount of caffeine absorbed. The sooner she vomits after ingestion the better. You can try getting her to vomit at home with 3% hydrogen peroxide. This doesn't always work and getting them to take it can be a challenge. The vet can give an injection that will cause her to vomit within minutes. If it has been more than 2 hours but not much more, the vet can give activated charcoal which helps to absorb the toxins in her intestines before her intestines absorb the toxins.
Caffeine toxicity can cause vomiting, diarrhea, a racing heart, excitability, tremors, seizures, cardiac arrhythmias and even death. If she is showing symptoms she should be taken to the clinic for observation and supportive care.