Is there one that is like an animated Lady Justice statue? I think that would be cool, possibly as a unique inevitable rather than a construct.
Ooh, that would be amazing! You can make a construct out of just about anything. Here's a template for Animated Objects: https://www.d20pfsrd.com/bestiary/monster-listings/constructs/animated-obje ct/
In terms of something premade, I'd suggest modding a Golden Guardian (https://www.d20pfsrd.com/bestiary/monster-listings/constructs/guardian-gol den/) to have a sword attack.
If you didn't want to go the construct route, I'd suggest an Outsider type, like an inevitable as you were thinking. But that you'd have to make from scratch. An Automaton might be a good balance of construct and outsider, if you're going to build her from the ground up.
I hope you find/create something that works!
Check out the Caryatid Column.
An Angelic Guardian might work.
YlothofMerab mentioned the Golden Guardian and Animated Objects.
The Terra-cotta Soldiers are very customizable.
Then you have the Waxwork Human for realistic creatures.
/cevh
None of those quite work because a. I wanted her to be sentient and all of those are mindless (except the terra-cotta soldier which has 1 int) and b. I figured she be LN and maybe even have some powers related to law and justice. (if this is the case, should she be an inevitable instead of a construct?)
A Gravenguardian (sorry my link fu is weak) https://aonprd.com/MonsterDisplay.aspx?ItemName=Graven%20Guardian
These are imbued by a specific deitie's power and have abilities based on domains. So, link it to your favorite justice deity and add an int score, voila!
That would work nicely! What should her scales do if anything?
Check soulbound doll, soulbound mannequin and soulbound shell.