It is common for vet office's to have free samples of Science Diet in their place.. They are not trained in this area> Someone did give you a link to the prem. foods and it is great. I did not know about S.D. being a bad food either unitil being on YT for a while. tHere are so many higher quality foods to choose from ! 
 Definately wait on the flea prevention meds. She is too tiny for them, and I would not take any chances . IMO.