Can't We Just Get Along?

My daughters are about three-and-a-half years apart in age. I really thought it would be a good age gap. My older sister is only 10 months older than me and we were never especially close growing up. I figured my little one would have a good role model and my older one would love teaching her little sister how to do stuff. Boy, was I ever wrong! I guess it's because they're on vacation from school and are feeling a little trapped in the house by the cold weather. One minute, they're nice. The next, it's like the WWF in here! It's crazy. The older one bullies the younger one, threatens her, says "I'm going to call your teacher." The little one retaliates and bullies back, egging on her older sister under she gets a smack or a kick or a scratch. Then, she comes crying about how her sister hit her. I consider myself pretty level-headed. My thought is - if you don't want her to hit you, stay away from her and don't goad her. But, she's four so she doesn't really get that rationale. You'd think they'd be happy to go outside today and make a snowman and snow angels and throw snowballs and go sledding. Nope. Fights about who the sled belongs to. They've been loving the dollhouse they got for Christmas. But, they fight about which doll gets to go inside and who gets to be the mom or the sister. I don't want to complain about my kids. I don't want to be the mom that prays for vacation to end and school to start back up. But, I am that mom. I just want peace. I know kids argue, but does it have to last all day? Do they have to call each other names and hit each other? Can't they be like passive-aggressive adults and bottle up their emotions and then take them out on someone else later in life? That's what I did! There are only three days left until school starts again. Then the fighting will only take place 5 hours a day instead of 12! Give me strength.