Newborn baby and feeding ...help, question?

So when im feeding Sometimes i can tell my baby is starting to use me as a "pacifier" but since she doesnt have a routine yet in feeding, (because i still just have colostrum.) i let her do it for a little while. My question is.. is she at least still getting milk? When i was in the hospital she nursed for like 2 hrs and the nurse said i shouldnt let her do that to much because she could start to hurt me pretty bad. BTW my baby is only 3 days old and a "snacker" so its hard for me to tell when she is done, unless she pulls away. (thats what i should do right?)