Katie hadn't seen Lavender since before the story broke. She was actually rather embarrassed. Not because it was her friend on the cover with the muggle prime minister. But that the paper that she worked for had put her friend in such a bad light in such a public way. Katie felt partially responsible for just being a employee of the paper!
Of course when Lavender owled her, she was going to come to her friend and the owl itself sounded urgent.
Apparating to the front door, Katie crossed the yard before going over and knocking.