This made me sigh a bit inside. So, actually, the alternate form was originally authored as one of the Dreamspawn heroes for a Hive Techtree Contest, and was later intentionally merged into the female demon hunter. It originates from the Spirit of Vengeance TFT Beta model, and that model had no alternate form despite inheriting obvious designs from the Reign of Chaos demon hunter model.
So, rather than having to delete mesh on your side, if you literally want the original model that was
merged into the Reforged hero as its alternate form, that original model can be found
here if you scroll down to "Hero Broker of Illusions". The color is different, but it's literally the ancestor of the file attached to this upload.