Katie's your new best friend, advisor, and person voted most likely to get you into trouble by all the other characters.
She's a Leo, so let's see what that implies for her.
Leos are likely to express themselves in dramatic, creative and assertive ways. They are also likely to enjoy the warmth of the physical Sun. Leos have great energy, courage and honesty. They are likely to be self-confident and maybe even a bit self-indulgent as they expect to be the centre of attention, and often are. Leos can be quite determined and usually get their way when they really want to. They also possess great integrity, and are a natural leader.
Leo people are very proud. Their challenge is to temper any tendency for arrogant or egotistical behavior and to instead develop humility and compassion; to learn detachment in the gift of their affections, so that they radiate their abundant energy freely and enhance the life experience of others around them.
I'm not certain if monsters stuck by any radiation of her abundant energy felt their life experience enhanced, but otherwise it checks out.
Katie's the tallest of the girls, and even 34C's look quite slim on her. A life of training combat has left her fit, though she doesn't have Bella's defined muscles.
She's part of the Clan, an extended (and often inbred) network of supernatural families stretching from the Border counties near England to the Highlands and Hebrides. Magic tends to blossom in the wild places of the world, the more industrialized a place gets the less accidental interaction between Elsewhere and our world there will be. In Bellanoch, where Katie's from, any old stone circle can serve as a gate into Elsewhere, but in Edinburgh you need expensive and rare magic portals to penetrate the barrier.