Poor girl. You can treat any open wounds with antibiotic ointment as long as it doesn't have pain relief - might help if things get worse.
I've seen a bruise like that only once and it was from a stuck malposition hatch that couldn't zip. Brushing generally takes a bit if time to show, so if it appeared shortly after the bloodmark, it could be from the same injury.
You say she has a place to run, but was she given a chance to acclimatize to the run before she was put in? She could have misjudged and run into the pallet while fleeing, or hit any number of things in a panic, like those pipe feeders since they protrude.
Integration should never be taken lightly. It takes time and 'observation' above all else. Without a roo, we have to be the ones to break up this sort of fighting, especially when space is limited.