Kat was called "stim-junkie" by Starbuck in "Scar." And the rivalry between the two pilots never really ended in "Scar"; I always took the ending to "Scar" as Starbuck grudgingly acknowledging losing that round to Kat, but not the whole war. Plus, if you go back to "Torn," I thought Kat and Starbuck was going to start slugging each other in the pilot rec room when Starbuck and Tigh were busy "bringing down morale."
Fact is, Kat and Starbuck went at each other because they were so similar. It took Kat's final sacrifice to get each other to show their respect.
EDIT: I have to admit that some of the looks back before the attack haven't worked out all that well in my mind, either. Not sure why. (Well, besides the atrocious "Black Market.")
EDIT x2: I don't think you're supposed to connect her drug-running past with her stim addiction. You don't hear about crack dealers getting hooked on pills.
EDIT x3: I must say, also, that the Cylon parts of the story are starting to feel like a drag, too.
Fact is, Kat and Starbuck went at each other because they were so similar. It took Kat's final sacrifice to get each other to show their respect.
EDIT: I have to admit that some of the looks back before the attack haven't worked out all that well in my mind, either. Not sure why. (Well, besides the atrocious "Black Market.")
EDIT x2: I don't think you're supposed to connect her drug-running past with her stim addiction. You don't hear about crack dealers getting hooked on pills.
EDIT x3: I must say, also, that the Cylon parts of the story are starting to feel like a drag, too.