It may be that she really does miss her brothers and the time spent with them. If so things should change when they return.
The other thought is that kids really don't know how to express anger or sadness, etc. Thus when they do get those feelings that can act out inappropriately. There are several great sets of books "the way I feel" aimed at the 4 to 7 year old child. They are meant to be read aloud (many times). And then to practice what the books teach. A good start might be "When I feel angry". It can be found here - http://www.amazon.com/When-Feel-Angry-Way-Books/dp/0807588970/ref=pd_sim_b_5
And if you scroll down, you can find several more appropriate books (like, the "way I feel" or "when I miss you") that would also be worth getting.
Hope this helps.
No she is at daycare because I am working....I would never put my child in daycare if I was SAH because I would miss them too much. We already have some one-on-one at home because of my boys. Both of my boys are special needs (one ADHD and the other Autism) and I have been working since she was born because I was still in the Army at the time, also my husband is her stepfather (her bio-father is non-existent pretty much), and I was a single parent for a period of time so that's why this is rather alarming. I would have expected this behavior during the diagnosis of ADHD with my younger son or when I was working as a single parent going to school, not now because I graduated about 6 months ago and I have focused all of my time on the kids since that ended. There really hasn't been any change the last couple of weeks other than her questioning of when my sons will return being pretty insistent. Like I said before this is completely out of character for her which is why I am concerned how this could develop so rapidly, and considering her brother's special needs I am very concerned that something is wrong medically but I don't want to jump the gun.
Yes her daddy does play with her and she has latched on to him since he has gotten here. The odd thing is that the daycare provider said that she only "acts out" when there are more than just a couple of kids there. We both spend a great deal of time with her and our only "alone" time is when she is in bed. Her sleep schedule is still adjusting because there is a two hour time difference between the two states.....heck I am still adjusting. I just found it rather peculiar because we started at this in home daycare when the lady first opened and its just been the last 2 weeks that she has been having problems. It is very uncharacteristic of her at all because she hasn't behaved this way ever.
Is she in daycare because you are working? If you are at home, possibly you could reduce the number of her hours at daycare and let her stay at home with you, for some one-on-one time with you alone.
When her daddy was away she got all the attention now he is back perhaps she shares you with him and also her other 'bro's are away , yes I do think that there is a connection.Does her Dad play with her, read to her, does he pay her attention .., could be she feels left out between you both and in fact is acting out.Focus on her positive side and praise her when you see her doing something right ....good luck