This is the Beta Sylvanas Reforged hero with the "upright" animations that was included in one of the early versions of Reforged Beta.
The model from Blizzard was in the binary MDX900 format and was translated to MDX1000 using Retera's Model Studio, which also reprocesses and reorganizes some of the internal structure of the model. So, this is not the original binary from Blizzard, and is instead a model file that will load in the Reforged Release client.
There is a second version of Beta Sylvanas that existed as a transitional version between this one and the one that is included in the Reforged Release. Because of that, I also can't rule out that there might have been different variations of this upright-standing Sylvanas in the Beta. It's hard to know for sure. Feel free to upload if you have a different preferred Beta Sylvanas model or whatever.
I didn't make this, I just opened it and pushed save in Retera's Model Studio -- which automatically converted it from MDX900 to MDX1000 format -- so in my opinion all credit goes to Blizzard Entertainment for the model.
Edit: I uploaded the Portrait with the same ported code run on it. But I don't actually know if it changed at all.
Edit: I think I fixed the portrait, first upload was busted.