John, is Janet normally a nervous dog? If there was no collar and no cage around, how is she?
I think it's normal for a dog to be cautious and even a bit reluctant to try something new. There are different approaches to handling their reluctance.
One way is to desensitize the dog to the fear. You do this slowly and over time. Let's use the collar as an example. Leave the collar out in an obvious place where Janet can reach it - maybe the coffee table - just leave it there for a couple of days, don't call attention to it. When the collar becomes a normal part of the "furniture", slip it on Janet's neck for 5 minutes (make sure it's very loose), then take it right back off. Increase the time until she's wearing it full-time (or whatever your goal is).
Not every dog needs to be treated like a delicate flower, dogs are pretty resilient. You know your dog well enough to decide whether you need a gradual, desensitizing approach or whether you can just slip the collar on the dog and say "you're wearing it and I don't want to hear another word about it
". The latter is my usual approach, but I know this method works with my dogs.
Dubh, my most recent dog, was very frightened of cars when we first found her. I'd put her in the back of my car to go to the vet and she'd shake. I pretended that I did not notice her shaking and kept talking to her about how fun it was to be in the car and what a good girl she was. After about 3 car rides, she suddenly fell in love with the car
! Now, if she sees me cleaning out the car she goes crazy wanting to go for a car ride
!
As WorldCitizen said, the dogs pick up on our energy
.