
I've had the occasional one of mine of things like Pred. but only short-term and to be honest, have never noticed any of the side effects you have been told your dog may experience. I kept them on the same amount of food, and if I noticed any weight gain, dropped it back a bit. I didn't notice any increase in hunger. If she's on reduced exercise, which she should be because once she's feeling more comfortable and perhaps moving more freely, she could do more damage to the joint, she may well not need as much food (put on weight!).
I think your vet has told you what your dog might experience, not what she will!!?
Hopefully she won't need to be on the antiinflammatories for long in any case - the discomfort from an arthritic condition can come and go, depending a lot on the weather...... I know I'm worse during cold damp weather than when it's dry ad warm. With those we had with this, in later life, we'd only treat them when they were having a flare-up.
Add @ Jo... PLT - wonderful. This was a life-saver when one of ours went off his back legs (spondylitis).