I am sorry to hear about this concern. Well, progesterone can be toxic to dogs. However, this tends to occur with large doses being ingested or repeatedly being exposed to it.
So, although she is smaller, she only got 1 tablet of the 100mg tablets.
To avoid all concern, you can induce vomiting since it was very recently ingested. More information below.
If you elect to wait, I would monitor for any bad diarrhea, loss of appetite, or appaering drunk-like (ataxic). If any symptoms of illness were to manifest, don't take a wait and see approach. Get to a vet for supportive care.
To induce vomiting at home, give 1 to 2 teaspoons for every 10 pounds of body weight of 3% hydrogen peroxide. ONLY use the 3% peroxide. If no vomiting within 15 minutes, the dose can be repeated. It is an irritant to the stomach lining, and that is why it causes vomiting. 1 teaspoon is 5ml of liquid.
Hope that information helps