Personality and Interest
Kate is the first of Luanne's deadbeat roommates to arrive after Luanne rents Pops' old house. Like the other roommates, Griffin and Tanya, she has little incentive to help out with the house expenses, and frequently blows off her responsibilities with ignorance or excuses.
Kate also seems to be addicted to talking on the phone as Luanne remarks when splitting up the bills that the phone bill is pretty much all hers, which Kate of course ignores. Ironically, she also seems to like the military as she carries a picture of a Marine (presumably her boyfriend) and wears a US Marine Corps sweatshirt in her scenes; this is ironic because the Marines and all military branches of the US military are built on order, discipline, and contribution, traits that Kate (and the other roommates) does not appear to have.
In the end, however, Kate ends up paying for her deadbeatness after a fed-up Luanne cuts off the house utilities in order to force her and the others to contribute their fair share of the bills.