I'm so sorry to hear that she was worse than you thought, but i'm glad she's on the road to recovery and back with her mummy now.
It must be horrible to have the illness that you have, but don't feel guilty, missing the occasional walk or having shorter walks is something all dogs have to put up with sometimes, and company is far more important to them. I hope having her back with you helps you to feel better too.
Playing stimulating games indoors with her when you can't manage a walk is a wonderful idea, and its amazing how tired they get from playing! Take people up on offers to walk her too, i know i'd love to walk another dog with Jarvis if i knew any other dog owners who needed help.
Wishing you both feel much better soon.