K.W.
Well you know the "why" she is acting this way, now you just need to figure out how to stop the behavior--especially since the "why" aka her baby sister and her father being away a lot is not going to change.
You already gotten some good advice, I think.
First, she is acting out negatively to get attention from ..period. And she does have a lot to deal with--her dad being gone and a new sibling to "share" the love of her mom. So you need to give her even more attention when she is behaving, and I agree, this means taking some time away from the baby to do so--maybe while the baby is sleeping since she takes more naps...or try and get a sitter once a week for a couple of hours so you can take her to the park, lunch etc. Play it up as "special mommmy and me time." And talk to her about herself, what she is feeling, etc.
Try to remain as calm as possible and not give in to her negative behavior with undo attention since she is doing it to get attention in the first place. If she becomes at all violent or angry with the baby though, have a time out structure in place--but make sure you talk to her about her feelings afterwards, and give her time to talk to you on a regular basis (maybe before bed) about her feelings regarding her sister, her dad, school whatever she wants to talk about, so maybe you can preempt some of these outbursts.
I also agree involving her in the care for the baby is also important--define her role as an older sister. Talk about what that means, and bring her in in any way possible with the baby's care--handing you wipes and diapers, helping with the bath--give her TONS of praise for doing so. She needs to feel important and being a big sister IS important.
Finally, if you do not see some changes, try seeing a professional family counseling that may be able to help. Does the military have these resources for you? Your hands are full with two little ones, so if the military doesn't offer support, check with your church, etc.