Hello and thank you for the question.
One Hershey Kiss is not a toxic dose of chocolate so your fur kid should be fine.
While this is not a toxic dose it may cause nausea so watch her for any vomiting or diarrhea. You can give 1 tsp of pepto or 1/4 tablet pepcid ac if she develops an upset tummy.
Please keep me updated and feel free to contact me if you have any further questions
Veterinary Technician
Practicing Veterinary Technician for 23 years. Veterinary Practice Owner, Technician Trainer