yup, keep on doing whatever you can to get her to exercise. i believe as well that as soon as she really does start to get the hang of it, she'll start to enjoy the play and exercise and her energy level will increase. it's the opposite of a vicious cycle then. our kitty doesn't like to be picked up, so i would make like i would do it and follow her around the house nice and slow and she would be forced to keep on walking just to get away from me. (i wasn't scaring her really! she was probably just a little annoyed. when she DID finally get sick of it, she knew she could just lie down on her blanket because i would never invade her space there and try to pick her up) if you have stairs where you live, that could be another good way to get a different kind of exercise. just bring her downstairs so that she has to go UP every once in a while to get to her food. good luck!
btw, this is just an fyi, but we have an 11 yr old who is 9 lbs and she gets @100 cals/day. our 14 yr old who is 15.5 lbs gets @150 cals/day. both mostly wet. the only dry food is the treats like greenies or pet greens. neither is REALLY active, but they do like to play when they can. they're certainly not couch potatoes and i think they're both very happy. maybe this will help you figure out how many cals to feed your baby.