I like the newer Jaina model. You can tell the stress of Theramore being destroyed has gotten to her in a lot of ways. Most of her hair goes gray and the style changed a bit. Her skin is now more pale and her clothing looks like its torn in a few spots. And with the eyes glowing like that im guessing she's so upset and angry that her full potential is now coming to the forefront and shes turning towards revenge and mass genocide of the horde for what happened to Theramore. She haas been said to be the most powerful mage on Azeroth and having her turn into something else like this is downright scary to be honest. She's basically tired of being nice and being a pacifist and damn anyone who interferes with her.
Heck i'd almost say shes going down the same road Arthas did in regards to hatred and being more evil.