Mood is very important, both for the results of anything you ask her to do, and for how she will develop and her overnight behavior. If the slave ends the day with a mood that is calm or better, that’s a good day. If she ends the day unhappy, that’s not good. In the short term, it may not matter, but as a general rule, bad mood = expect problems. She is more likely to try to escape, fight you, or become depressed and eventually suicidal. Of course, she will only try to fight you if she believes she has a chance. Your relative stats compared to her, particularly strength, fighting skill, and the overall strength of your aura (if you use auspex on her, you can see whether your aura is stronger than hers) affect whether she will fight you seriously or not. Of course, she may also fight you when you try to punish her physically, so stick to verbal punishment (or “passive” punishment like taking away her bedroll) if you are a weakling… You can also go spar at the colosseum to build up your strength and fighting skill, but this is entirely optional.
Besides rewards, you can improve her mood by giving her certain clothing, making sure she is clean (spa or baths if you aren’t living in the slums), and having her do her favorite activity (if she has one). Don’t neglect the “ask questions” interactions with the slave, they can give you useful hints. If the slave is refusing to answer, that just tells you that you need to work on their obedience more.
This is for you, too,
Abecalp
As a last resort, a slave can’t bother you overnight if she is in a dungeon cell or frozen in cryo storage. If you aren’t sure how to fix the situation, you can always freeze the slave for 1 spark/day and work on another one. With loans and guild contracts, it’s usually possible to get another slave…