Occam: Well, let's be honest, Katia went out of her way to (unintentionally) insult other Khajiit at every turn. So she was already likely to get a bad disposition against her. Further, remember that by her own words Rajirra heavily implies that she turned to a life of crime and shady near-crime by necessity, which definitely gels with the lore. It seems to have made her bitter. Also, she was definitely sure that Katia was gonna die and trying to make sure that the imp didn't get out, and the coverup was probably to prevent whatever Sigrid might reserve for screw-ups (real or imagined). Which overall does make her a presumptuous bitch, but a mundane one, not a villain. And in light of the fact that everyone not mentioned elsewhere is going to get murdered by scamps pretty soon, probably, we can probably cut an ordinary bitch some slack; one just hopes that she gets told off and does something right before likely dying...