Tasambeker had great feelings for Jobel even though he insulted and humiliated her. When Davros took over Tranquil Repose as "the Great Healer", he turned it into a breeding ground for Daleks and used hidden cameras to watch the funeral home, observing Jobel and Tasambeker.
He offered to have her work directly for him, and they used the cameras to see Jobel conspiring against Davros with Takis and Lilt. He wanted Tasambeker to serve him with her total being and he would allow her to become a Dalek: it was an offer she couldn't refuse. To show him her total obedience, she had to kill Jobel.
She confronted Jobel and offered to help him escape Tranquil Repose, claiming that Davros lied and that he didn't care about Tranquil Repose. He wouldn't listen to her and she killed him by stabbing him with a syringe after Jobel insulted her.