Hi!
Congrats on your baby. Your little one sounds right on track. She is doing the things she should be! It is funny about the laughing. My DS laughed ONCE at 4 months and no matter what I did I couldn't get him to do it again until months later! He smiled alot, but I told my hubby that maybe we are just not that funny.

Now at 11 months he laughs all the time and even laughs in imitation when we do.
If you are ever concerned about development or just want to know what to look out for, there are many developmental checklists on the internet. Just type in "developmental milestones" into your browser and you should get tons of info. Be careful though, because baby's development can vary widely. Always ask your pedi too.
Have fun with your LO!!!