Oh poor sweet Dusty. It's so hard to tell if they're in pain isn't it. I'm afraid I don't have any advice, but you should let her be where she wants to be, even if you have to carry her upstairs. Glad to hear she's eating and wants to play, if only for a short time. I think the heated cat bed is a very good idea, that might help ease the pain. You're such a good kitty mom, and I do hope you'll find a medicine that helps her.

Lots of kisses to Dusty, and hugs to you.