My daughter has had3 strep throat infections in 3 months, she is 4. could this be more indicative of more serious infection?

Doubtful: Sounds more to me like she is around someone who is a carrier and unaware. It is possible you or another household member carries the bacteria in your throat but has no symptoms. Then, if she drinks from you cup, eats a bite off your spoon, takes a sip from your soda, she can re-infect herself. Also make sure you have bought her a new toothbrush after treatment each time. Make sure all med is taken.