What level of sadism is in the game? Per example, can you slap her in the face?
Sadism in the game is currently split into 4 categories.
1: training
You can hurt Ruby (slaps, punches, strapped palms, wedgies, and caned ass) as part of her training sequences.
2: reward / punishment
You can currently punish Ruby with 3 degrees of severity, focussed on spanking (hand and tool) in a stress position and tied over a desk.
Ruby can develop masochistic tendancies, and be rewarded with escalting levels of pain and abuse which range from a light spanking to severe treatment.
3: sexual
You can currently hotdog Ruby, this can be done with the intent to hurt her, and on a more badly bruised backside for increasing levels of pain.
You will also (currenrly in development) be able to go down a CNC roleplay path with Ruby, which will allow you to be violent with her; mixing beatings (including slapping and punching at this point) or blackmail with sex acts.
4: aftercare
While most of Ruby's aftercare options are positive reinforcement or neutral, you can also be intentionally cruel to her (forcing her to strip and re-dress in an ice cold shower in the gym, or do lines while painfully wedgied in the classroom).
Currently the most cruel thing you do is probably the pre-cnc beating, but she'll willingly ask for more violent things than that if you develop her masochism enough.
Get her horny, and masochistic, enough and you can shove a thumb covered in electric shock (or agonising burning sensation causing) gel up her butt, turn her into a complee pain goon and she'll orgasm so hard her brain basically turns off while you do it.