C.P.
One thing I have notices with my 7 year old, is that with my son, she wants to be able to do everything that he is doing. I believe that it is all the attention you are showing to the baby. We had a really bad incident with my son about 2 weeks ago. He decided to take a header off the fireplace border. Had to go to the ER. The next afternoon, My daughter runs in the house after falling off her bike saying she needs to go to the hospital just like Lane (her brother) Try getting him involved with helping take care of the baby. That way you are spending time with him too. Also remember that he is in that "Terrible Two" stage.
C.