Yes they can. But every single other test she's had, bar none, has shown that she's PVS.
She's been asked to give a clue with her eyes. It's a time honored, classic test. She can't pass it.
She's a woman, not a vegetable
But not to fret. Looks like another delay by the Dems, so she'll probably be well on her way to dehydration before anything is done.
But she hasn't had all the more valuable tests to make that determination.