Of course females CAN get along, its just a risk. Many people will tell you not to have two intact females (I know plenty of people with two fixed females). You just have to have a large enough home to where you can separate them if things happen like what you're describing.
Most likely...they will not outgrow this behavior. If they're "randomly" fighting they will keep doing it. Unless you really monitor them and see what sets it off, it won't stop. In this case it seems like food and other high value items do it. So just don't give them bones or anything else they might feel like guarding.
The issue with random fights is that you can never trust them alone together. What if you weren't there to break them up? One of your dogs would be dead.
So when people say don't get two dogs of the same sex, its because in general its a bigger risk. You don't know for sure that they'll get along, where as most male/female combos might battle once or twice for hierarchy but then settle down...and even then usually one takes control without a fight.
CD RE TC HIC 7/10