How to fix kaisa's V neck.
Seriously just add a freaking scar to her chest and everyone will be happy. Personally I don't care if she has V neck or not but people seem to and from artist's perspective, yea I can see it's not a good design.
So maybe make it seem as if she didn't always have a V neck but it was ripped open by say a monster, it's not like the scar has to be all bloody either. Just a light pink scratch mark would do the trick. It would make her design have more sense yet not demand any huge changes to the model (and it would be easy detail to add to her splash).