I'm so sorry your sis and you are going through this. I hope treatment is easy and effective for her. Her response is totally normal. I felt that way too.

There are gynecological cancer support groups in many areas that she might find helpful. If she's in the US the American Cancer Society can help with low-cost lodging and transportation costs.

Many care clinics have a social worker who helps connect patients with services and guidance in navigating the process and smoothing out bumps in the road.

My cancer is a little different than endometrial (endocervical adenocarcinoma), but the treatments probably share some similarities.

If your sis's body starts to not process fluids fast enough for her daily external radiation appointments (presuming she has to do that) ask about getting hydration therapy via the picc or port.

The steroids they gave me with chemo made it difficult to sleep the night of chemo. I asked my oncologist for something. He gave me lorazepam. It wasn't what I had in mind (I was thinking more like Ambien), but it did help and, on reflection, Ambien probably wouldn't have helped much.

You're supposed to eat a high protein diet and not lose weight in order to protect your kidneys (and maybe liver?) during chemo (at least with Cisplatin), but that's easier said than done when you can barely keep anything down. If she really loves a particular food she might want to avoid it during chemo.

There are cancer supporter / care giver support groups too that you might find helpful. Care givers and other close loved ones get sort of forgotten in all this, caring for their person while carrying their own physical and emotional burdens. So be kind to yourself too. <3