https://playskate.com/f401 Can be a lifesaver.
I would invest in some sensory bins, art supplies like markers, stickers, stamps, pretend toys, especially small stuff like plastic figurines or barbies that she can hold in her hands.
Lots and lots of books, especially board books she can turn pages herself.
Musical instruments like shaker eggs, small horns and do a daily dance party so she can move and be active to the extent that she can.
Also if there is anywhere you can hang a hammock that is a great way to let her do something fun that feels normal (swinging in a swing).
Be prepared for her to regress and be clingy and emotional. Some people find babywearing (well, toddlerwearing) helpful so she can be close to you and comfortable and feel like she is participating and it is totally possible in a spica cast.
Diapering was the hardest part for us.