While thinking about Vi as a schoolgirl (like the others), I immediately had the thought that she could be some kind of delinquent ruffian instead of a law enforcer.
The look for her costume was tricky...I started with something girly closer to the established Star Guardian skins and while a skirt would definetely be something new for a Vi skin it doesnt quite work for her since she's still regarded as a tomboy. So it went through quite some changes and tests until the final version was established.

The pet was easy in comparison! Vi is strong, sporty, fast and confident and her pet should be nothing like that.
Similar to Rainbow Dash and Tank from "My little pony".

here's a link to the official LoL board thread:
https://boards.na.leagueoflegends.com/en/c/skin-champion-concepts/XvP61f9d-skin-idea-star-guardian-vi