
Sad to say your hubby is actually rewarding her for being frightened by giving her attention
You need to ignore the behaviour you do not want(the hiding)& reward the behaviour you want with cuddle, praise, treats etc
Look at the hoover from your puppy's point of view, it's probably 10 times bigger than her & makes a noise that she cannot see where it is coming from
So as has been said leave her crate door open so she can get away to a place she feels safe & don't hoover too close to her. Then leave the hoover out where she can see it but where she doesn't have to get too close to if she doesn't want to.
You can try to put treats near the hoover for her not too close at first but find a distance she is happy with & very very gradually work your way closer so that she associates being near the hoover with reward. You can also push the hoover around switched off so that she only has sight of it & if she stays put or ignores it praise her & talk to her(anything you like using a silly voice too )
If her breeder has used a hoover near her it probably wasn't the same make/model & looked & sounded differently to yours. When I got my first Dyson my GSD who is bomb proof(I thought) hated it but by ignoring her bahaviour that I didn't want & praised her when she ignored it pulled her round & she now totally ignores it
She may never like the hoover but can learn to ignore it or just move away when it is around being used. to somewhere she feels safe