Is my daughters nose broke despite the x-rays coming back negative?

Even though the nasal bones do not appear fractured on the x-ray, cartilage can become fractured and displaced away from the bones themselves. Cartilage grafting such as a spreader graft may be required if the upper lateral cartilage has been fractured off the nasal bone. It is best to have this done within the first month after the injury, rather than waiting for it to heal crooked. For many examples please see the link below

An x-ray is typically not needed to diagnose a broken nose. Go see a plastic surgeon or facial plastic surgeon as soon as possible for an evaluation. The bones may not be broken but the cartilage may be damaged and cause the nose to look bent to one side - this will not show up on an x-ray. If you wait too long, it is harder to fix and get insurance to cover it.