Mail girl, from my own personal experience, I felt no major effects from my radiation sessions for a couple days, then I mostly felt very tired. (My treatments were for breast cancer. ) I see no reason why she couldn't have a pedicure at this time. Boy, I sure do wish someone had planned a special day for me like you are doing for your Mom. Believe me, she will be thrilled to have something other than the hospital to think about!!! I refer to that phase of my cancer treatments as 'life in the basement'. LOL
One thing you might consider doing is shopping together for a really good skin cream, like one you might use for sun burn, maybe one with aloe in it. I found this to be very helpful in nourishing the radiated skin when it becomes dry and red. Be sure to ask her doctor first though if they recommend using this type of product.
PS, if you would like to email me about your Mom , please do so, my email address is in my profile. Or you could PM me. I will be happy to answer any questions at all about my own experiences.
Hugs and many prayers, Mariposa
God bless you and hang in there kiddo.