I mean, they're trying to get intel there and Kfufu isn't really prompt to help so of course they need to deceive her to get what they need. Kfufu isn't someone they could sugarcoat and have her saying what they want to hear. Trust me, they wouldn't get anything out of Kfufu if they didn't use such method.
They are dumb enough to bring the enemy into their base.
It's dumber to kill someone they can get intel off. And where did you want them to bring her anyway ? Anywhere on Earth will put at risk to have Sigma trying to get her back and have some civils casualties. Having Kfufu in her base is the safest option they have.