At a loss

My mum has been diagnosed with metastatic bladder cancer. She has mets on her lungs, kidney, liver and lymph nodes. She has had 3 rounds of Padcev and Keytruda. Hey forth got postponed because her liver enzymes shot up. She has been admitted to hospital because it looks like she is dehydrated and has an infection. She has lost well over two stone in weight and hardly eats anything because she has lost her appetite. Her oncologist has now brought her scan forward to see if the treatment is doing anything and if not they will look at a different option. I guess what I’m asking is can the treatment still be working even though she looks so poorly and could all of this stem from her lack of food and water?? What will be the next steps if the treatment hasn’t done anything or the cancer has gotten worse? Is a scan after only 3 rounds of treatment long enough to even tell? Any answers you can provide would be really helpful as I’m struggling at the minute x