Worried about a new nurse at a hospital where I work.

I work at a small hospital on a Med/Surg floor. We have a new nurse there, a RN who seems to just completely space out. She has a very flat affect. Sometimes she will walk thru the nurses station, stand in the same place for at least 5 minutes and just stare off into space. When she does talk to me, she seems very nice, but the contact is usually asking me the same questions over and over. I can't tell if it is a mental problem or drugs. I worry about the patients that she cares for and I have noticed that when she gets her assignments they are usually the easier pt's. The charge nurses and director have recently been made aware of this, but so far nothing has been done/
I dont know if this would go under career advice or be better to be placed in the general nursing discussion?