For the last 3 days she has been hiding.
She is not eating and does not come when called. I finally found her in
the closet and now she is under the bed. Do you have an idea what is
going on?

Get her to the vet asap. Not eating and hiding are signs that she's sick. Of
course, if there were some major psychological turmoil in the house, a young
kid staying at your house, a new animal, a new friend that hates her, that
might cause that same behavior. Has anything major changed? If not, off to the
vet. My cat didn't eat and hid. I took him to the vet. He was diagnosed with
stomach/liver cancer and died in two days.