I'm glad Pidgie came downstairs and is reclaiming her post. I wonder if she might also be losing muscle mass from not moving around as much in addition to a reaction to the meds. I suppose there is not much to be done about that though. Do you think Dr. Lee would allow you to give her NutriCal? It is a paste that has 2,500 calories (I think) per dose and comes in a tube like hairball remedy and is of the same consistency. I've used it on one of my cats and they all gather around trying to get some so I think it's proably tasty too.
Prayers that she stops losing and at least maintains the weight she has.