I have had platelet count of 1. My hematologist looks at symptoms along with numbers. I had no symptoms so I took 20mg prednisone and drove home. Predinsone is my rescue treatment. I started on Nplate then because you don't want to be on steroids long term- too many side effects.
I am on weekly Nplate. I don't appear to have any side effects from it. It is similar to Promacta except it is an injection. My counts are usually between 20-38, not normal counts at all. If I go below 20 I don't worry about it. Its not necessary to be over 100, just a safe count which is above 20 or 30 for most people. Although for a couple years my counts were in the teens and often below 10. I learned that I am okay with low counts. The treatments can be as bad as low counts for doing harm. Your doctor sounds like she knows to not over-react to low counts. And to not over-treat. Promacta is a good drug with an 80% success rate to bring counts up to a safe level. Also some people go into remission on Promacta and Nplate meaning they can stop taking the drug.
When I was new to ITP 12 years ago, I went to the ER with a count of 6. The doctors looked at me like "Whats wrong with you?" They were looking at symptoms. I sat there for 4 hours then was sent home with prednisone and was told to call a hematologist. That visit cost me $2500. and took me 2 years to pay it off. I will never go to the hospital for ITP again. Nurses have begged and threatened me to get me to the hospital for a platelet transfusion. My count was 7, I refused and was totally fine. You will get to know your body and symptoms and become able to judge your own risk tolerance.
Another thing that helped me is to learn about the "clotting cascade". There are around 50 chemicals that assist with blood clotting. Clotting is too important for the body to rely on platelets alone. So when there are not enough platelets, the other chemicals can take over to some degree. That is not to say that there is no risk but its just to say that your body can compensate so thats why we look at symptoms also.