I am so sorry for you and your Mum are having to go through this. The oncologist should be able to give you information about how important chemo may be to your Mum's chance of staying cancer-free. They can give you the statistics for people who have similar pathology to your Mum.
As the other ladies have said it was just bad luck that your Mum got an infection. I was hospitalized for 3 days with an infection and neutropenia during my chemo last year. After that I had the Nuelasta injection 24 hrs after each chemo and I did not have any more problems.
Feeling so sick will definitely affect your mood. Also the drugs they give you with the chemo can also affect your mood. It may not seem like it but chemo does only last for a short while and the long term benefits for me made it worthwhile. It is the toughest thing I have ever had to do but I am well now and have a much better chance of staying well because of the chemo.
There are medications that can help with just about all the side effects. The oncologist should be able to advise and give you scripts for what your Mum may need. I had medication for diahorea, constipation, oral thrush, nausea, heartburn, sore eyes and pain. I did not always need them but knew they were there if needed.
Using Biotene mouthwash and toothpaste can help your mouth. Manuka honey sooths the throat. Hygiene is critical, I washed my hands constantly and had frequent showers. I made sure everyone around me washed their hands too and kept hand sanitizer in my bag for when I went out and had to touch things like door handles, trolley handles etc.
Talk with the oncologist and get all the help you can. Use this network to keep in touch with others who have been through this too. My daughter was my main support when I went through chemo. I could not have done it without her. I will never be able to do enough to thank her for what wonderful support she gave me. Thinking of you and wishing you and your Mum all the best.
Take care. Deanne xxxx