I'm a first time mom and my newborn is a week old and she bumped her head on her crib. She seems to be ok though she's sleeping a lot but I don't know?

Get evaluation. It is unlikely that a 1 week old could have caused a bump on her head on her own, a one week old can't roll. This situation is concerning for some ptential physical abuse and looking at the fact that the mother is 18 y/o raises the risk. Please take this child to the doctor for an evaluation immediately, it may save a life.