Sounds to me like it is her temperament. She might be very sensitive. And yes the baby could be adding to her outbursts. That being said, she will need skills to cope with situations without breaking down and that is where you come in. Sympathize.."I know you would like to go outside but right now I cannot do that but you can choose to play with your tea set or your cars." If she is still upset you can say, " I see that you are upset and that is O.K. When you are ready to talk about it let me know and we can find a way to make you feel better/solve this problem/come up with a solution. Your daughter may learn to step away for a bit, be sad, then deal with the situation. All in all be sensitive but you do not have to give in. If her emotions get loud tell her that she can be upset but if she chooses to be so loud she needs to find an alone place like maybe her room to be sad and loud because it is hurting your ears. If she would like to be sad quietly ( quietly not silently) she may stay where she is. Sometimes we all just need to step away to deal with our emotions. As for sleeping, you cannot MAKE someone sleep but you can have her stay in her room. Maybe she can read books or listen to music or books on tape. Let her know that she does not have to sleep but she must stay in her room until what ever time is decided. She will most likely fall asleep anyway so no worries.
B. Davis
Child And Family Coaching
http://www.ChildAndFamilyCoaching.com