Agreed she is a cunning, calculating, dominating character, but her previous looks were what made her desirable, the new look just leaves her at all her personality characteristics minus that desireability.Oh, come on... She just has a different hair style and makeup in the new scene. And it makes sense. Women, especially those who care about their appearance, don't wear the same clothes, hair style and makeup at home, at work and on special occasions (and it was a very special occasion for Karen).
And actually in the game Karen is portrayed as a cunning, calculating character. In the scene with the teacher, the drinking scene, in that scene at the MC's house. Everywhere. Even the voice acting is chosen to depict her this way.
Ofcourse they change, but they all have a personality, characteristic appearance, which reflects through all the changes and different looks. The point is this new appearance is at a stark contrast to her previous one and not for the good, in fact opposite of good