The vets I work for are extremely cautious about everything (they never even offered the Pro Heart injection because they were wary of it - thank goodness for that because they were right) but they allow puppies to be on Frontline and feel comfortable with it. We've never had any problems at the clinic or at the shelter with treating the puppies. We do have tons of fleas and ticks here in Texas though. If there aren't many where you live, then it might not matter so much if you wait. If you feel comfortable with your vet's recommendations, then stick with those. I just wanted to tell you that if you do treat her, it will be fine as I've never seen any pups have problems with it. The Frontline box and website even state that its safe for puppies.