Can a Dental Hygienist damage a Crown by using the wrong tools and working to much on it?

it is highly unlikely that your hygienist damaged your crown.  Extra time was likely spent on that tooth due to potentially having more inflammation of the gums here,  especially  if your crown has metal in it.  Have your dentist take a look.  Good luck.  

The tools used are supposed to be the same ones used on other teeth.  It is possible for her to damage your crown in other ways, like scratching the surface of the crown through over aggressively trying to remove plaque.  However, the situation that you described does not sound like this occurred.  If it appears that you have a gap along the top of the tooth, it's likely that that gap was there all along, but covered with plaque.  At most, the hygienist just removed that plaque.  I hope this has helped ease some of your concerns.  Feel free to follow me on RealSelf if you have more questions.

Chances are the hygienist didn't. Damage your crown. It's possible the gap feels bigger because there was something stuck to the crown. I suggest returning to your dentist to have them take a quick look at the area.