oh yeah, sword boi is a pretty big hypocrite here for saying torture is bad, except when he does it. ( in his defence though he only ever tortures confirmed criminals, but its still a dick move )
The only reason I can see why she hasn't gotten it would be that it's hard to get skills, Master being able to effectively give skills makes training the skills a ton faster.
But for normal people training new skills takes a lot of time.
But it could also just be plot armour, it's a very real possibility...
I actually found the first time the torture skill appears in the novel ( chapter 123 - Luzerio ) Master actually points out its the first time he has seen the skill.
The thugs that she meets is back in chapter 87 (it's actually called "A Pair of Grunts." ) and they don´t actually have that skill.
So if it makes you feel any better, that dialouge doesn't happen in the novel and is something the manga adaptation added in
Just for context, chapter 123 is in the next arc, once they arrive back on land in the next city. ( 85-100 is the "twins on a boat" arc and we are on 91 or so...)
Novel chapters are padded out a lot because of the frequent use of inspection.