It depends a lot on what chemo drugs are in her regimen. With my first round of FolFox 5F/U, they were giving me Dexamethasone steroids as part of the regimen. My neuropathy got so bad in my hands and feet I was almost debilitated. Turns out, the steroid can cause permanent to semi-permanent neuropathy. Some of what I'm going through will be lifelong and will never recover...I've lost all feeling in my fingertips and the soles of my feet have been on fire for nearly two years now.
I have since demanded all steroids be removed from my regimen...to the chagrin of my oncologist, but it hasn't gotten worse, and, in fact, the treatments are actually easier without the steroids.
You'll have to talk to your Doctor and/or care team to find out for sure, but there are definitely side effects that can be permanent...oncologists seem to not want to discuss these possibilities, or they choose to minimize the potentially permanent impact some of these side effects can have on a person.
My first year I worked with an oncologist that didn't seem to want to explain anything. I, finally, on the advice of a friend, got a second opinion, and now have an oncologist and care team that listens and is willing to adjust my meds as needed to reduce some of the more serious side effects. Do not be afraid to keep pushing your mom's oncologist to make adjustments to make her more comfortable...