No one of the girls got a bad concussion and bruises. The other girl got a chef’s knife and a hatchet to defend them and was arrested. The people who beat up the other girl presumably were not arrested. People don’t usually carry knives in Britain, but the kitchen knife and hatchet were probably in her house.
It was filmed in a residential area, so yes, they probably got the knife and hatchet from their apartment...it’s not likely they were walking around all day holding them.