Good evening - I'm Dr. Sara. I'm a licensed veterinarian and I work exclusively with dogs and cats.
Vomiting that many times in a row so soon after a potential ingestion of something like an exterminator applied product is certainly a little alarming. If you can get the active ingredient in the product that was applied, I would be happy to research it and see what I can come up with.
With acute onset vomiting, as long as their breathing is not labored, there is no abdominal distention, and their gums are pink and moist, I usually recommend holding off on giving any food or water for at least 6-8 hours. If they are continuing to vomit though this time, it's time to see the vet. If they stop vomiting, then I start by offering a small portion of water. If they keep that down for more than 2 hours, I offer another small amount of water and a small taste of food (1-2tsp). As long as they continue to tolerate small meals, you can gradually increase the amount of food at each sitting and increase the time in between meals. If they aren't eating at all for >24 hours, this also merits a trip to the vet.
My dosage for pepcid is 0.5mg per kg of body weight - however I cannot guarantee 100% that this will be safe as I don't know exactly what she ingested, it is quite likely to be helpful.
Please let me know what other questions I can answer for you :)