7 weeks old and still not smiling

My daughter was born at 36+2 so I’m not sure if adjusted age is important in this scenario or not. I guess it’s getting to me that women always talk about how their babies smiled at 5/6 weeks. My daughter is now 7 weeks and still isn’t smiling. Sometimes I think she is trying to smile but I don’t know. She does coo sometimes. I just need some reassurance that this is normal at this stage I guess. I know every child is different but I can’t wait to see her beautiful smile and know that she is developing properly.