I've seen reports that Vortex sometimes corrupts the downloads, so you might want to check and redownload the mods you're using for her.
This might be an item variation conflict (floating head sounds like it), if you've redressed her into another modded clothing item or installed another armor mod mid-playthrough. A list of installed mods is required to pinpoint any incompatibilities. First try redressing her into some vanilla robe, if it looks normal then her modded equipment (whatever she had on when this happened) certainly conflicts with something else.
A sudden floating head/no head might also indicate a corrupted .utc file that you unknowingly installed with another mod pack / NPC overhaul mod (although, that's more likely to happen on a completely new playthrough rather than mid-playthrough as all equipment is backed into your save as soon as you enter a new location). Try looking through your Documents\BioWare\Dragon Age\packages\core\override or wherever Vortex stuffs the mods for any .utc files with her name and deleting them, then start a new game or at least find a save in/before Ostagar where you haven't yet entered the Corcari Wilds.
Also, a floating head instead of armor sometimes shows up on modded items, if you haven't patched your exe with the 4 GB Patch.