My girl Zari had four chemo treatments before the second oncologist agreed with me that she did not have cancer and we stopped them (long story, she has some unknown autoimmune thing that they know what it isn't but not what it IS)... so I know how SHE handled chemo. Zari did great with it, she didn't need to be sedated, she was okay in the smaller cages they have at the vet. Zari is quite handleable though, she was a show cat before she got ill, but she's wriggly like a Savannah is if you try to hold her still...if that gives you some idea of what she is like. When she was ill she was easier of course, when she was having the chemo she had next to no blood cells nor bone marrow cells. She was a very sick cat. Now she is phobic about the vet, she hates being there and it is a tussle to get her regular blood tests done. I am grateful they don't insist on sedating her for them though!
My opinion is that it will greatly depend on quality of life...how easily she is treated and how your girl does on the chemo drugs as they are not all the same. Zari had 8 hour Cytarabine IV infusions, and we gave twice daily oral Cyclosporine as well. She also got prednisone which is what she ended up taking for a year for whatever was wrong with her. Zari did not seem to have any ill effects from the chemo, she was so ill before though so the fact that she was slowly recovering might well have masked that? I don't know. With her treatments she started eating, and being more social (she was hiding away) and generally seemed better for it.
With your girl Sen, I would likely just see how one or two treatments go for her, how this impacts her having to spend that time at the vet and how it affects her body. If overall she seems better with it, then it is worth doing to have those days/weeks/months with your precious girl. If it basically is torturous for her, then the kindest most loving thing you can do is to help her not suffer anymore.
I am so sorry for the diagnosis, my heart goes out to you.