We had "refitters" change our tub into a shower. It was a bit too expensive but worth it, I was afraid of slipping and it's scary to think of hitting the tub rim (ours had sliding doors for the shower part and "rails" which would have really hurt!)

I'd get a really long shower wand/hose and a "smaller" container she could at least get most of her legs, etc. in while sitting on the toilet seat or somewhere comfy and take a good sponge bath? until your brother or other friend/relative has time to help you with a permanent solution?