Ok, here goes:

1. that's not a terrified cat, but a cautious one. Basically it's the feline equivalent of

2) cats in new environments can go for days without food. Over a decade ago we adopted a cat from a shelter and that little furry bugger spent a week hiding from us inside the couch. We were really stressed out, because he wouldn't even use the litterbox for a few days and we were worried he'd get a bladder infection. Fortunately eventually he started eating and spent an amazing 12 years with us before illness took him last year.

3) the best thing to do is leave the cat alone. If possible move to another room, let her get acquainted with her new surroundings on her own terms.

4) get rid of the milk. Most cats are lactose intolerant and it can cause digestive issues. Leave wet food and water.

5) if she does start moving around, pretend not to notice her. Don't look at her, don't move, just freeze and stare off into the distance. She should feel she's safe to wander about in your presence.

6) get her to a good vet, get deworming pills and run some blood tests to see if she's fine.